Novichok, a Soviet-era nerve agent, was used to poison former Russian spy Sergei Skripal and his daughter in Britain.
Britain accused two Russian men of trying to murder Sergei Skripal and his daughter Yulia.
Britain last week charged two alleged agents of Russia’s military intelligence agency in absentia with the poisoning of former Russian spy Sergei Skripal and his daughter Yulia.
Alexander Petrov and Ruslan Boshirov are charged in absentia with conspiracy to murder, attempted murder and use of the nerve agent Novichok.
The testing is part of the investigation into the Novichok deaths of Dawn Sturgess and Charlie Rowley.
A man and a woman in the UK have fallen ill after being exposed to novichok, the deadly nerve agent used in an assassination attempt on a Russian spy earlier this year.
The pair were hospitalized after being found unwell just a few miles from where an ex-double agent was attacked in March.
A man and a woman are in a critical condition after they were exposed to an unknown substance near the southern English town of Salisbury.
Britain has accused Russia of being behind the nerve agent attack, but Russia has denied any involvement.
An international chemical weapons group's analysis confirms British tests on the poison -- and further points to Russia as the culprit.