OPCW releases 5th report to identify perpetrators of chemical weapons use in Syria

Originally published by the OPCW

The Secretariat of the Organisation for the Prohibition of Chemical Weapons (OPCW)’s fifth report concludes there are reasonable grounds to believe that the Syrian Arab Air Forces were the perpetrators of the chemical weapons attack on 1 October 2016 in Kafr Zeita in the Syrian Arab Republic. The comprehensive investigation was conducted by the Investigation and Identification Team (IIT) from March 2024 to December 2025.

Based on the analysis and corroboration of the all obtained information, the Secretariat concludes there are reasonable grounds to believe the Syrian Arab Air Force dropped at least one yellow pressurised cylinder, which hit a cave system in the Wadi al-Aanz valley in Kafr Zeita. The pressurised cylinder impacted near two ventilation openings near the Al Maghara Hospital. The cylinder then tumbled down and came to rest near the entrance of the cave system. Upon impact, the cylinder ruptured and pressurised released chlorine gas, dispersing through the Wadi al-Aanz valley, injuring 35 named individuals and affecting dozens more.

The Secretariat reached its conclusions based on the standard of proof known as “reasonable grounds”, a standard consistently adopted by international fact-finding bodies and commissions of inquiry. The assessment included information from the Fact-Finding Mission (FFM), States Parties, interviews conducted by the IIT, and analyses of samples, computer modelling, satellite imagery, front-line maps, authenticated videos and photos, and other relevant data. This information was considered holistically and OPCW procedures were strictly adhered to. The Secretariat also thoroughly considered the positions put forward by the former Syrian authorities but was unable to obtain any concrete information supporting those positions. To date, five reports identifying perpetrators have been issued by the OPCW on seven cases of use of toxic chemicals as weapons in Syria.

OPCW Director-General Ambassador Fernando Arias said: “We welcome the assistance received from the new Syrian authorities, marking the first cooperation by the Syrian Arab Republic with an IIT investigation. These actions are in line with the commitments made by President Ahmad al-Sharaa, when I visited Damascus in February last year. This represents a significant milestone and a meaningful contribution to international accountability.”

“This new report provides further evidence of a pattern of systematic use of toxic chemicals as weapons by the former Syrian authorities against their own people. The report and its findings are now in the hands of the international community, the United Nations, and the States Parties to the Chemical Weapons Convention. The Secretariat will continue its investigations to identify perpetrators of chemical weapons use in Syria through its Office of Special Missions,” he added.

The full report can be read here FIFTH REPORT BY THE OPCW INVESTIGATION AND IDENTIFICATION TEAM