In the spring of 2015 a Syrian major general escorted a small team of chemical weapons inspectors to a warehouse outside the Syrian capital Damascus. The international experts wanted to examine the site, but were kept waiting outside in their car for around an hour, according to several people briefed on the visit.

　　When they were finally let into the building, it was empty. They found no trace of banned chemicals.

　　“Look, there is nothing to see,” said the general, known to the inspectors as Sharif, opening the door.

　　So why were the inspectors kept waiting? The Syrians said they were getting the necessary approval to let them in, but the inspectors had a different theory. They believed the Syrians were stalling while the place was cleaned out. It made no sense to the team that special approval was needed for them to enter an empty building.

　　The incident, which was not made public, is just one example of how Syrian authorities have hindered the work of inspectors and how the international community has failed to hold Syria to account, according to half a dozen interviews with officials, diplomats, and investigators involved in eliminating Syria’s weapons of mass destruction.

　　A promise by Syria in 2013 to surrender its chemical weapons averted U.S. air strikes. Many diplomats and weapons inspectors now believe that promise was a ruse.

　　They suspect that President Bashar al-Assad’s regime, while appearing to cooperate with international inspectors, secretly maintained or developed a new chemical weapons capability. They say Syria hampered inspectors, gave them incomplete or misleading information, and turned to using chlorine bombs when its supplies of other chemicals dwindled.

　　There have been dozens of chlorine attacks and at least one major sarin attack since 2013, causing more than 200 deaths and hundreds of injuries. International inspectors say there have been more than 100 reported incidents of chemical weapons being used in the past two years alone.

　　“The cooperation was reluctant in many aspects and that’s a polite way of describing it,” Angela Kane, who was the United Nation’s high representative for disarmament until June 2015, told Reuters. “Were they happily collaborating? No.”

　　“What has really been shown is that there is no counter-measure, that basically the international community is just powerless,” she added.

　　That frustration was echoed by U.N. war crimes investigator Carla del Ponte, who announced on Aug. 6 she was quitting a U.N. Commission of Inquiry on Syria. “I have no power as long as the Security Council does nothing,” she said. “We are powerless, there is no justice for Syria.”

　　The extent of Syria’s reluctance to abandon chemical weapons has not previously been made public for fear of damaging international inspectors’ relationship with Assad’s administration and its backer, Russia, which is giving military support to Assad. Now investigators and diplomatic sources have provided telling details to Reuters:

　　- Syria’s declarations about the types and quantities of chemicals it possessed do not match evidence on the ground uncovered by inspectors. Its disclosures, for example, make no mention of sarin, yet there is strong evidence that sarin has been used in Syria, including this year. Other chemicals found by inspectors but not reported by Syria include traces of nerve agent VX, the poison ricin and a chemical called hexamine, which is used to stabilize sarin.

　　- Syria told inspectors in 2014-2015 that it had used 15 tons of nerve gas and 70 tons of Sulphur mustard for research. Reuters has learned that inspectors believe those amounts are not “scientifically credible.” Only a fraction would be needed for research, two sources involved in inspections in Syria said.

　　The head of the Organization for the Prohibition of Chemical Weapons (OPCW), the international agency overseeing the removal and destruction of Syria’s chemical weapons, conceded serious questions remain about the completeness and accuracy of Syria’s disclosures.

　　"There are certainly some gaps, uncertainties, discrepancies," OPCW Director General Ahmet Uzumcu, a Turkish diplomat, told Reuters.

　　But he rejected criticism of his leadership by Kane and some other diplomats. Kane told Reuters that Uzumcu should have turned up the pressure on Syria over the gaps in its reporting and done more to support his inspectors. Uzumcu countered that it was not his job “to ensure the full compliance” of treaties on chemical weapons, saying that the OPCW was mandated to confirm use of chemical weapons but not to assign blame.

　　Syria’s deputy foreign minister, Faisal Meqdad, insisted that Syria was completely free of chemical weapons and defended the country’s cooperation with international inspectors.

　　“I assure you that what was called the Syrian chemical weapons programme has ended, and has ended with no return. There are no more chemical weapons in Syria,” he told Reuters in an interview.

　　Sharif did not respond to requests for comment about the incident at the warehouse.

　　SARIN ATTACK

　　On Aug. 21, 2013, hundreds of people died in a sarin gas attack in Ghouta, a district on the outskirts of Damascus. The colorless, odorless nerve agent causes people to suffocate within minutes if inhaled even in small amounts. Assad’s forces were blamed by Western governments. He has repeatedly denied using chemical weapons and blames insurgents for the attack.

　　In the wake of the atrocity, the United States and Russia brokered a deal under which Assad’s government agreed to eradicate its chemical weapons programme. As part of the deal, Syria joined the OPCW, based in the Hague, Netherlands, promising to open its borders to inspectors and disclose its entire programme – after previously denying it had any chemical weapons.

　　Syria declared it had 1,300 tons of chemical weapons or industrial chemical stocks, precisely the amount that outside experts had estimated. In an OPCW-led operation, costing hundreds of millions of dollars, that stockpile was shipped overseas for destruction with the help of 30 countries, notably the United States.

　　But there were two significant problems. First, inspections did not go smoothly. Days after the Ghouta sarin attack, OPCW inspectors heading for the area came under sniper fire. They made it through to Ghouta eventually and were given just two hours by Syrian authorities to interview witnesses and take samples. The team confirmed that sarin had been used.

　　And in May 2014 a joint United Nations-OPCW convoy was hit by explosives and AK-47 fire while attempting to get to the site of another chemical attack in the northern town of Kafr Zita. That mission was aborted. On the return journey some of the team were detained for 90 minutes by unidentified gunmen. Syria’s foreign ministry issued a statement blaming terrorists for attacking the convoy.

　　Reuters was unable to determine exactly how many times the work of inspectors has been hampered, but Syrian tactics have included withholding visas, submitting large volumes of documents multiple times to bog down the process, last-minute restrictions on site inspections and coercing certain witnesses to change their stories during interviews, four diplomats and inspectors involved in the process told Reuters.

　　The OPCW team has carried out 18 site visits since 2013, but has now effectively given up because Syria has failed to provide sufficient or accurate information, these sources said.

　　The second problem was a switch of tactics by Assad’s forces. While the United Nations and OPCW focused on ridding Syria of the stockpile it admitted having, Assad’s forces began using new, crude chlorine bombs instead, according to two inspectors. As many as 100 chlorine barrel bombs have been dropped from helicopters since 2014, they said. Syria has denied using chlorine.

　　Although less poisonous than nerve gas and widely available, chlorine’s use as a weapon is banned under the Chemical Weapons Convention that Syria signed when it joined the OPCW, an intergovernmental agency that works with the United Nations to implement the convention. If inhaled, chlorine gas turns into hydrochloric acid in the lungs and can kill by drowning victims in body fluids.

　　A source involved in monitoring Syria’s chemical weapons for the OPCW said Damascus began using chlorine as “a weapon of terror” to gain a battlefield advantage when one of its bases in Kafr Zita was threatened with being overrun in 2014.

　　“The base was surrounded by opposition. The government forces wanted to depopulate the area. That’s why they started using chlorine,” said the source.

　　A senior official who has worked with United Nations and OPCW investigators said two helicopter squadrons dropped chlorine barrel bombs, drums filled with chlorine canisters, from two air bases. To produce such a quantity must have required technical staff and logistical support, suggesting the operation was overseen by senior commanders, the official said.

　　The introduction of a new type of chemical weapon came at an awkward time for the OPCW, said the source involved in studying Syria’s chemical weapons for the weapons monitoring group. It was keen to remove Syria’s declared stockpile and reluctant to start a probe into alleged government violations that could jeopardize Syrian cooperation. The goal of removing the stockpile, which Western governments feared could fall into the hands of Islamic State, took precedence over the chlorine attacks, the source said.

　　OPCW head Uzumcu denied there had been a reluctance to investigate reports of chlorine attacks, pointing out that in 2014 he set up a fact finding mission to look into them. This mission was not tasked with assigning blame, however. It concluded that the use of chlorine was systematic and widespread.

　　Uzumcu said the team’s conclusions were handed to the OPCW executive council. It condemned the use of chlorine and passed the findings to the United Nations. A spokesman for the United Nations said it was the role of the OPCW to determine whether or not a member state was in breach of the chemical weapons ban.

　　Kane, the former U.N. high representative for disarmament, told Reuters that Uzumcu should have tackled Syria over its lapses in reporting to the OPCW, including undeclared chemicals and a failure to report the government’s Scientific Studies and Research Centre, which was, in effect, the programme’s headquarters.

　　“Why, my God, three-and-a half years later, has more progress not been made in clearing up the inconsistencies? If I was the head of an organization like that ... I would go to Damascus and I would confront these people,” Kane said.

　　Uzumcu said the OPCW was constrained by its founding treaty, the 1997 Chemical Weapons Convention. The OPCW has no obligation to act when one of its members violates the convention, he said. Determining blame for the use of chemical weapons is the task of a separate United Nations-OPCW mission in Syria, the Joint Investigative Mechanism, established in 2015. A spokesman for the Joint Investigative Mechanism referred questions to the OPCW.

　　“The secretariat has fulfilled, accurately and entirely, the tasks they were asked to fulfil and will remain within our limitations as far as our mandate is concerned,” Uzumcu said.

　　He said some states have suspicions that the Syrian government hid stocks of chemical precursors that might be used for the production of certain nerve agents, including sarin. But he said there was no conclusive evidence.

　　Uzumcu said he regretted that relations had broken down between Russia and the United States on the OPCW executive council, which has the power to impose restrictions on Syria’s membership and report it to the U.N. Security Council for non-cooperation.

　　Uzumcu said his office was still seeking answers from the Assad administration about undeclared chemicals, aerial bombs and the Scientific Studies and Research Centre, which has overseen Syria’s chemical weapons since the 1970s. Syrian officials have maintained that no supporting documentation exists for the programme, which included dozens of storage, production and research facilities.

　　POLITICAL DEADLOCK

　　The Syrian crisis has had a profound effect on the way the OPCW operates. For two decades the organization had reached consensus on most decisions, only calling on the 41-member executive council to vote on a handful of occasions. Syria marked a clear divide on the council.

　　In 2016, when an inquiry by the United Nations and OPCW found that Syrian government forces were responsible for three chlorine gas attacks, the United States sought to impose sanctions on those responsible through the executive council, but then dropped the proposal, the details of which were not made public. A text drafted by Spain condemned the attacks but removed any reference to sanctions. It was supported by a majority, including Germany, France, the United States and Britain, but opposed by Russia, China, Iran and Sudan.

　　The United States has since placed sanctions on hundreds of Syrian officials it said were linked to the chemical weapons programme. President Donald Trump ordered a missile strike on a Syrian air base, but division on the OPCW governing body and at the United Nations has prevented collective action against the continuing attacks.

　　Western governments accused Moscow of trying to undermine investigations by the United Nations and OPCW in order to protect Assad; Syria says the inspection missions are being used by Western countries to force regime change.

　　Russian officials did not respond to a request for comment.

　　SARIN FOUND

　　Former U.N. chief weapons inspector Ake Sellstrom, who is now chief scientist for the U.N.-OPCW mission, said it is critical that perpetrators of chemical attacks are put on trial to deter future use of weapons of mass destruction. His team should be reporting back to the U.N. by mid-October, he said.

　　A key unsolved question is what happened to the 2,000 aerial bombs that Syria said it had converted to conventional weapons, a process that would be costly and time-consuming.

　　“To my knowledge, the Syrian government never furnished any details of where, when and how they changed the bombs’ payload,” said an OPCW-U.N. source, who took part in investigations in 2015-2016. He said there clearly was “a real, high-level, command structure behind this.”

　　Syrian officials did not respond to requests for comment about the bombs.

　　The team is also examining the deaths of almost 100 people on April 4 when a gas attack hit Khan Sheikhoun, a town in the rebel-held province of Idlib near the Turkish border. Samples taken from people exposed to the chemicals and tested by the OPCW confirmed sarin use. Meqdad, Syria’s deputy foreign minister, said in the interview Syrian forces were not to blame, repeating earlier denials by Foreign Minister Walid al-Muallem.

　　Sellstrom said the presence of sarin so long after Syria was supposed to have dismantled its chemical weapons programme posed difficult questions. “Is there a hideout somewhere, or is there production somewhere and how much is available?” he said, adding that the reported use of aerial bombs in Khan Sheikhoun could point to the Syrian forces keeping some strategic weapons as well.

　　The attack means either “that someone can produce sarin today, or sarin has been hidden,” Sellstrom said.

　　PHOTO CAPTION

　　A U.N. chemical weapons expert holds samples from one of the sites of a chemical weapons attack in the Ain Tarma neighborhood of Damascus in August, 2013.

　　REUTERS