Inspectors from the Organisation for the Prohibition of Chemical Weapons (OPCW) are due to start work in Douma, outside the Syrian capital, Damascus.
The alleged chemical attack on April 7 2018 is the sixth chemical attack in Douma in 2018. Munitions recovered from previous attacks show they are modified Iranian 107mm rockets.
In addition to collecting samples, OPCW inspectors will be looking for other clues to confirm the alleged use of banned toxins in the attack on April 7.
Analysis of the samples will take place at the OPCW’s central laboratory in the Netherlands. The evidence is split and sent to independent national laboratories affiliated with the OPCW.
The inspectors will also be looking for other evidence, such as canisters, rocket or bomb fragments, impact sites and craters and will take photographs and video of them.
The OPCW Fact-Finding Mission will not assign blame.
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