AMSTERDAM (Reuters) - Inspectors with the global chemical weapons agency on Wednesday visited a second site in Syria’s Douma and took samples to help them determine whether banned toxic munitions were used there.

The Organization for the Prohibition of Chemical Weapons is investigating the deaths of dozens of people in the enclave outside of the Syrian capital on April 7.

The attack led to air strikes by the United States, France and Britain against sites in Syria. They accused the government of President Bashar al-Assad of using chemical weapons, possibly a nerve agent. Syria and its ally Russia have denied the accusation and said rebel forces staged the attacks.

The fact-finding mission (FFM) arrived in Damascus on April 14, but was delayed by a week before it could get to sites it deemed of interest.

Western powers accused Russia and Syria of stalling tactics to delay the process and of tampering with evidence that may have pointed to government involvement.

Samples taken from two sites will be returned to the OPCW’s laboratory in the Netherlands and then sent on to affiliated laboratories for examination, the OPCW said in a statement. Those tests will determine whether or not chemical weapons were used.

The OPCW does not assign blame for chemical attacks and there is currently no mechanism that can do so after Russia vetoed a resolution to extend the mandate of a United Nations-OPCW mission in November.

The Russian delegation to the OPCW will hold a briefing on Thursday in The Hague at which it will present “some Syrians to speak about the reported Douma incident”, the agency’s statement said.

It was unclear who Russia planned to have speak, but the OPCW said they have not been interviewed by investigators.

“The FFM will continue to carry out its independent and impartial mission based on interviews with relevant people, its findings from the site visits, analysis of the sample results, as well as any other information and materials collected,” it said.