He went on to say that the information about the alleged use of chemical weapons in Syria usually emerges amid reports of the Syrian army's successes, adding that it was Saturday night when a large number of militants with members of their families were evacuated from Douma.
The British delegation to the organization called for the inspectors to be given "unfettered access" to Douma, adding that "Russia and Syria must cooperate". "It is our understanding the Russians may have visited the attack site", US Ambassador Kenneth Ward said at an OPCW meeting in The Hague.
The attack on April 7, prompted military strikes on Syrian government targets by the US, Britain and France a week later.
In the fraught aftermath of the suspected attack in Douma and the West´s response, Washington also prepared to increase pressure on Russia, Syrian President Bashar al-Assad´s main ally, with new economic sanctions.
British, Russian and French ambassadors were all seen arriving at the headquarters of the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague.
The attack, which killed more than 40 people, has drawn worldwide outrage and prompted the USA and its allies to consider a military strike on Syria, something Moscow has strongly warned against.
Deputy Foreign Minister Faisal Mokdad said several coordination meetings were held with the OPCW team but he did not provide any further details as their schedule.
Russian military officials were at the site of the Douma attack days before the OPCW reached Damascus, leading to fears that the site might have been tampered with.
Despite polls showing scant support for the move, May said it had been her "responsibility as prime minister to make these decisions", while Macron also defended his move as part of his constitutional powers.
Soussan reiterated a pledge by the Syrian government that the chemical experts would be allow to investigate unimpeded.
OPCW inspectors have been attacked on two previous missions to the sites of chemical weapons attacks in Syria.
The trio of Western powers that carried out the strikes warned they would repeat the operation if Damascus used chemical weapons again, while Russian President Vladimir Putin warned any fresh strikes would "provoke chaos".
Regime forces have since entered Douma and declared the entire Eastern Ghouta region around it fully retaken, ending a five-year siege and reclaiming an opposition bastion on the edge of the capital.
Even though the OPCW team was not allowed in, the Syrian authorities organised a tour of the town for the foreign press, including AFP.
But "strangers entered as we were in a state of chaos and spread a rumour among people there had been a chemical attack, and people became alarmed".
The commander of Russian Radiological Protection Troops Igor Kirillov said on Monday that footage of the alleged chemical attack in Douma was deliberately staged and that the so-called evidence was "fake".