A high purity form of Novichok , a nerve agent developed in the Soviet Union in the 1980s, was used to poison former Russian spy Sergei Skripal and daughter Yulia Skripal, an international chemical weapons watchdog group confirmed on Thursday, leaving little question Russia was behind the act.

The Organization for the Prohibition of Chemical Weapons said tests on the substance confirmed the British governments identification of Novichok, a military-grade poison. The organization didnt identify a suspect in the poisonings.

There can be no doubt what was used and there remains no alternative explanation about who was responsible only Russia has the means, motive and record, U.K. Foreign Secretary Boris Johnson said .

Skripal and his daughter were found unconscious on a park bench on March 4 in the British city of Salisbury. The U.K. government, which determined that Novichok had been used to poison them, condemned Russia for the act of aggression. Russia denied responsibility, prompting Prime Minister Theresa May to expel 23 Russian diplomats from the U.K. More than two dozen Western countries announced similar expulsions, prompting the Russians to retaliate by ejecting diplomats.

Skripal remains critically ill. Yulia Skripal, who was released from the hospital on Tuesday, released a statement Wednesday asking for privacy and rejecting any assistance from the Russian embassy in the U.K.

I, too, am still suffering with the effects of the nerve agent used against us, she said. I find myself in a totally different life than the ordinary one I left just over a month ago, and I am seeking to come to terms with my prospects, whilst also recovering from this attack on me.