April 3 (UPI) -- British scientists said Tuesday they can't prove whether Russia was the source of a nerve agent used to poison a former Russian spy and his daughter in Britain.
Gary Aitkenhead, chief executive of the Defense Science and Technology Laboratory at Porton Down, said the poison used in the attack against Sergei Skripal and his daughter Yulia Skripal in Salisbury was identified as as a military-grade novichok nerve agent, but couldn't determine its origin.
"We have not verified the precise source, but we have provided the scientific information to the government, who have then used a number of other sources to piece together the conclusions that they have come to," Aitkenhead said.
He added the agent requires "extremely sophisticated methods in order to create, something that's probably only within the capabilities of a state actor."
Aitkenhead said the British government reached its conclusion that Russia was responsible for the attack by combining the laboratory's scientific findings with information from other sources and stressed Prime Minister Theresa May was always aware Porton Down's assessment was "only one part of the intelligence picture."
He also denied Russian claims that the nerve agent came from Porton Down, which is located 8 miles away from Salisbury.
"There's no way that anything like that would ever have come from us or leave the four walls of our facilities," Aitkenhead said.
Aitkenhead's comments came before Russia was set to convene for an emergency meeting of the Prohibition of Chemical Weapons in The Hague.
Russia has denied any involvement in the poisoning and has posed 41 questions to Britain and international watchdogs about the nature of the attack and the subsequent investigation.
"We certainly reject any notion or claim of Russian involvement in the Salisbury incident. We will not tolerate this kind of irresponsible and basically indecent behavior on the part of the British government. They will have to answer for that," Russian Ambassador to Ireland Yury Filatov said.