A Ministry of Defense spokesperson told CNN on Thursday that the scientists had conducted the tests in British labs on blood and hair samples from victims, collected at Khan Sheikhun in Syria's idlib province, where 89 people were killed in the April 4 gas attack.
The worldwide body on chemical weapons control is testing samples from a suspected nerve gas attack that killed at least 87 people in Syria last week and could produce a report on the matter within three weeks, the British delegation to the commission said Thursday.
The report comes one day after Russian Federation vetoed a Western-backed U.N. Security Council resolution demanding a speedy probe into the Khan Sheikhoun attack.
Moscow is a key ally of the Syrian government, and has intervened militarily on its behalf since September 2015.
The United States responded to the gas attack by firing 59 cruise missiles at a Syrian regime air base. No one has yet visited the site of the crime.
Mr Rycroft was speaking during a UN Security Council meeting to discuss a resolution put forward by the US, UK and France, which, as expected, was vetoed by Russian Federation. "How do you know that?"
Moscow has stood by Syrian regime leader Bashar al Assad, saying the poison gas belonged to rebels, an explanation Washington dismisses as beyond credible.
The U.S. -led airstrikes targeted the big depot containing chemical materials in the town of Hatleh in the eastern countryside of Deir al-Zour on Wednesday, said the army in a statement.
The Syrian government has denied responsibility for the alleged toxic gas attack in rebel-held Idlib province last week, following which the USA retaliated by targeting a government airbase.
According to a military report on Syrian state TV, a USA -led coalition airstrike on Wednesday hit poison gas supplies belonging to the so-called Islamic State, killing "hundreds including many civilians", Reuters reports.
Syrian authorities have repeatedly denied using any chemical weapons. Abu Laila who is with Deir Ezzor 24 activist group that has reporters throughout the eastern province that borders Iraq also denied there was such such an airstrike.