Gary Aitkenhead, chief executive of the Defence Science and Technology Laboratory (DSTL) at Porton Down, told Sky News they had not been able to establish where the novichok nerve agent used to poison Sergei and Yulia Skripal was made.
Gary Aitkenhead, chief executive of the Defence Science and Technology Laboratory at Porton Down, told Sky News that researchers were able to identify the substance used in the attack against Sergei and Yulia Skripal as a military-grade nerve agent known as Novichok, a class of chemical weapons developed by the former Soviet Union and Russian Federation.
"There's not - as far as we know - any antidote that you can use to negate the effects of it", Aitkenhead said of novichok.
He said that the creation of the Novichok agent would have required "extremely sophisticated" methods likely only to be available to a state actor.
Mr Aitkenhead said blame had been laid at the door of Russian Federation because of other information available to the British government.
On the basis of which characteristics ("markers") has it been ascertained that the substance used in Salisbury "originated from Russia"?
Skripal and his daughter have been in hospital since ingesting the deadly nerve agent novichok in Salisbury, Wilts on March 4. Why was it not the case with the Skripals?
Lavrov said Monday that Russian Federation had requested the OPCW meeting to discuss the case and asked it to provide details of its cooperation with Britain in the poisoning probe.
Russian Foreign Minister Sergei Lavrov on Monday suggesting that the British government may be behind the poisoning to distract attention from problems around Brexit.
"We hope that during those discussions a full stop will be placed on [the issue of] what happened" to former spy Sergei Skripal, Mr Putin said in Ankara ahead of the meeting on Wednesday of the Organisation for the Prohibition of Chemical Weapons (OPCW).
Oklahoma teachers hold second day of walk-out protests
The numbers may be smaller in the second day event as teachers from smaller, rural districts may not be able to take part. But Priest said teachers reject the argument that there isn't enough money to provide additional funds for classrooms.
Marcher hit by police vehicle while protesting shooting of Stephon Clark
Protesters and officers also had a brief standoff near a highway ramp, before protesters changed direction. Sacramento County Sheriff Scott Jones blamed "paid protesters" for causing the chaos during the rally.
Pinwheels raise awareness of Child Abuse Prevention Awareness Month
A pinwheel garden was planted in Jackson's Austin Blair Park Monday to raise awareness about child abuse prevention. Residents are encouraged to recognize a parent, sibling, teacher, or anyone who helped them during their childhood.
"It is our job to provide the scientific evidence of what this particular nerve agent is, we identified that it is from this particular family and that it is a military grade, but it is not our job to say where it was manufactured", Aitkenhead said.
"This is only one part of the intelligence picture".
The spokesman concluded, "It is our assessment that Russian Federation was responsible for this brazen and reckless act and, as the global community agrees, there is no other plausible explanation".
He argued that experts have said that such nerve agents could have been made in some 20 countries.
A top Russian diplomat says the nerve agent poisoning of a former Russian spy may have been arranged by Britain to justify military spending.
Yulia Skirpal, 33, is now awake and alert, stoking hopes that she could offer details crucial to cracking a case.
Her father remains in a critical but stable condition.
Britain and two dozen of its allies have expelled over 150 Russian diplomats. The United States charges that the 60 Russians that it targeted are intelligence officers operating under diplomatic cover.
Russian Federation has responded in kind with an equal number of expulsions.