International inspectors found previously undisclosed chemical weapons materials in Syria more than a decade after the country agreed to dismantle its arsenal, according to a late May report from the Organisation for the Prohibition of Chemical Weapons (OPCW).
The agency said the findings included chemical munitions such as aerial bombs and rockets, production materials, and thousands of pages documenting the program under former Syrian President Bashar Assad.
The discoveries came as Syria’s security structure shifted after the December 2024 collapse of the Assad government. A recent Pentagon watchdog report said the transition was increasingly unstable and that new Syrian government forces had quickly taken territory previously held by the Kurdish-led Syrian Democratic Forces, a U.S. partner in the campaign against the Islamic State group.
By mid-April, U.S. troops had withdrawn from several bases and transferred control to Syrian government forces, ending a 10-year presence in the country. The Pentagon report said Syria’s new authorities would likely struggle to control the country’s fragmented security apparatus, especially as the Syrian Democratic Forces integrated into a national armed force. It also warned that those conditions could allow Islamic State to regroup.
Against that backdrop, OPCW investigators said the full scope of Syria’s chemical weapons program might still be unknown. Information gathered since December 2024 indicated that more than 100 additional sites might be linked to the program, up from 26 previously known locations.
The OPCW said inspectors found the same types of aerial bombs used in chemical attacks on Ltamenah in March 2017 and Khan Shaykhun in April 2017. Earlier investigations found that jets dropped sarin and chlorine in Ltamenah and sarin in Khan Shaykhun. Investigators also found the same type of rockets used in the 2013 chemical attack in Ghouta.
Since March 2025, inspectors had visited more than 20 sites across Syria, many previously inaccessible under Assad.
The Pentagon watchdog report said at least 150 Islamic State fighters escaped detention facilities during the Syrian government offensive as Syrian Democratic Forces guards redeployed. It also said disorder increased at camps and detention centers holding families linked to the group. The United States transferred more than 5,700 Islamic State detainees to Iraq, but about 20,000 people left al-Hol camp without monitoring.