A former Russian spy convicted of passing information to British intelligence agency MI6 was found unresponsive at a British shopping center Sunday, along with a woman, and both remain in critical condition.
The pair were exposed to an unknown substance but showed no visible signs of injury.
Sergei Skripal, 66, was granted refuge in the UK following a "spy swap" between the US and Russia in 2010.
He and a woman, 33, were found unconscious on a bench at a shopping centre in Salisbury on Sunday.
Authorities have yet to identify the substance but indicated there was no risk to the general public.
They have declared a "major incident" and multiple agencies are investigating. They said it had not been declared as a counter-terrorism incident, but they were keeping an "open mind".
Skripal is a retired Russian intelligence officer who was imprisoned for 13 years in 2006 for spying on behalf of the U.K.
He was convicted of passing the identities of Russian intelligence agents working undercover in Europe to the UK's Secret Intelligence Service, MI6.
Russia said Col Skripal had been paid $100,000 for the information, which he had been supplying from the 1990s.