"The samples collected will be transported to the OPCW Laboratory in Rijswijk and then dispatched for analysis to the OPCW’s designated labs," the OPCW said in a statement.
"The OPCW will evaluate the situation and consider future steps including another possible visit to Douma," the organization added.
The mission is investigating an incident that took place in the town on April 7: What the West considers a chemical attack conducted by the government, Moscow views as a provocation carried out to justify a strike on the country.
Footage presented by the White Helmets has been proven fake by a boy who was filmed and his father, as well as another boy who got food for participating and a doctor at Douma's hospital where the shooting took place. Russian servicemen have found no trace of any attack at the site, but discovered a militant laboratory equipped for manufacturing chemical weapons.
The Russian General Staff had correctly predicted a false flag attack with ensuing aggression against Syria a month before it actually occurred.