April 16 (UPI) -- The Russian government on Monday denied tampering with the site of a suspected chemical attack in Syria before investigators could enter the area.
Investigators from the Organization for the Prohibition of Chemical Weapons have not yet gained access to Douma, where the deadly attack occurred a week ago, OPCW Director-General Ahmet Üzümcü said.
Kenneth Ward, U.S. ambassador to the OPCW, said "it is our understanding" that Russians may have visited the site of the attack.
"We are concerned they may have tampered with it with the intent of thwarting the efforts of the OPCW fact-finding mission to conduct an effective investigation," Ward said.
Russia has denied interfering, saying the OPCW needed U.N. permission before they could travel to the area.
"Everything comes down to the lack of agreement from the U.N. secretariat's department for the OPCW experts to travel to Douma, where the events took place," Russian Deputy Foreign Minister Sergei Ryabkov said.
Monday, Russian Foreign Minister Sergei Lavrov also denied interfering in Douma.
"I can guarantee that Russia has not tampered with the site," Lavrov told BBC News.
In response to the attack, U.S., British and French forces fired 105 missiles at three sites in Syria early Saturday morning. Russia and Iran, both allies of Syrian President Bashar al-Assad, have condemned the strikes.
Russian officials have said the attack was staged.
"I cannot be impolite with the heads of other states but you quoted the leaders of France and the U.K. and U.S. and, frankly speaking, all the evidence they quoted was based on media reports and social media," Lavrov said.