Chemical weapons inspectors collected on Wednesday more samples from the Syrian town of Douma, three weeks after a regime chemical attack in the area that left at least 40 people dead. Making a second visit to the area, they collected samples from a new location hit by a gas attack on April 7. The Organization for the Prohibition of Chemical Weapons said all the evidence collected in Douma will be brought back to its labs on the outskirts of The Hague. "They will be split and dispatched for analysis by the OPCW designated labs," the body said. An earlier visit took place on Saturday after the inspectors were delayed for days from getting to the town, just east of Damascus, over security reasons. The delay prompted accusations that Russia and Syria may have tampered with evidence at the site. The United States, France and Britain have blamed Bashar Assads regime for the chemical attack. The three countries struck Syrian chemical weapons facilities in joint airstrikes a week later. The OPCW visit to Douma and sample collection would allow the international watchdog to proceed with an independent investigation to determine what chemicals were used in the attack. The watchdog is not mandated to apportion blame for the attack. The mandate of a joint UN-OPCW body delegated to investigate who may be behind such attacks has expired and Russia has vetoed its renewal. The joint body had found the Syrian regime responsible for several previous attacks. The OPCW also confirmed that Russian diplomats are organizing a briefing on Thursday in The Hague for OPCW member nations and would "bring some Syrians to speak about the Douma incident". It has advised the Russian delegation that "these persons should be first interviewed" by the inspectors who are currently in Damascus. It was also recommended that such a briefing take place once the fact-finding mission has completed its work. The Russian embassy in the Netherlands said in a tweet that the briefing would involve "witnesses from Syria who were at the staged videos of #WhiteHelmets" -- a humanitarian organization made up of some 3,000 volunteers working in rebel-held areas.