The alleged chemical weapons attack on April 7 was used by the US, Britain and France to justify an attack last weekend against targets which they called essential for Syria's chemical weapons program.
May said it would in any case be hard to attribute responsibility for the Douma attack because Russian Federation had vetoed a United Nations attempt to extend investigatory powers. The town has been besieged as the government has been fighting to oust rebels from the greater eastern Ghouta region, just outside the capital of Damascus.
"Cleaning up a site after a chemical attack to the point where no traces of the agent or of characteristic degradation products can be found is hard, in particular when the impact site was a building". The government-run Syrian Central Media said the missiles targeted the Shayrat air base in Homs.
OPCW Director-General Ahmet Uzumcu told a meeting of the organization's Executive Council on Wednesday that the team will not visit Douma until United Nations security experts, who came under fire in the town on Tuesday, deem it safe and only if the team "can have unhindered access to the sites".
British Prime Minister Theresa May accused the Syrian government and its ally Russian Federation of trying to cover up evidence and obstruct the investigation. Packing its bags and vacating the playing field to the likes of Russia, Iran, and Hizballah is escapism masquerading as strategy.
In response, the United States, France and Britain conducted unprecedented missile strikes on Syrian military installations, but Paris admitted on Tuesday they were a matter of "honour" that had solved nothing. Israel did not confirm or deny the allegations.
"It is our concern that they may have tampered with it with the intent of thwarting the efforts of the OPCW Fact-Finding Mission to conduct an effective investigation", he added.
Worldwide investigators on Tuesday entered a Syrian town hit by an alleged chemical attack, after days of delay and warnings by Western powers that crucial evidence had likely been removed.
If chlorine was used in the attack as alleged by the western alliance then much or maybe even all of it will have evaporated in the ten days since the incident.
Earlier Monday, Russian deputy foreign minister Sergei Ryabkov said the inspectors could not go to the site because they needed approval from the UN Department for Safety and Security.
The team will interview emergency responders, survivors, medical staff who treated victims and other witnesses to determine whether they suffered from symptoms associated with chemicals.
Activists on the ground in Syria said the attack killed more than 40 people and injured hundreds more sheltering from bombing in basements beneath the city.
Alexander Rodionov of the Russian military's chemical weapons protection unit said its experts found chlorine and components for producing mustard gas at a rebel laboratory in Douma.
Given that 11 days have passed since the attack, some chemicals might be harder to trace.
The recent attack in Douma has killed up to 75 people, and injured over 500 people. The fact that USA leaders weren't ready to wait for inspectors to do their job indicates they wanted to make a military statement, and didn't want it to be clouded by whatever the inspectors might find.
Syria and Russian Federation have both denied that Syrian government forces carried out the Douma gas attack, suggesting it may have been staged to implicate them.
The Syrian government had told the team that they could not accompany them because a ceasefire agreement prevented them from entering the area.