A man fighting for his life after being exposed to an unknown substance is allegedly a former Russian spy who was given refuge in the UK.
Sergei Skripal, who is 66, was granted refuge in the UK following a "spy swap" between the US and Russia in 2010, the BBC reported.
Police and paramedics discovered a man and woman, thought to be in their late 20s to early 30s, in a critical condition in Salisbury, Wiltshire, on Sunday afternoon.
The woman, who was unconscious, was airlifted to Salisbury District Hospital, while the man was taken by ambulance.
And after the pair were admitted to the accident and emergency department, the hospital was forced to shut it down and call in the fire service and an Incident Response team to decontaminate the area.
Wiltshire Police confirmed the two incidents were linked, saying the man and woman had been 'exposed to an unknown substance'.
Firefighters and police attended The Maltings shopping centre in Salisbury at around 4.15pm yesterday afternoon.
Officers taped off an area around a bench where one of the pair had been sick.
A specialist chemical response unit removed the unknown substance from the area, wrapping it in several protective layers.
Police said the substance would be destroyed, along with the protective suits.
A police spokeswoman said: 'Wiltshire Police and partners have declared a major incident after it is suspected that two people have been exposed to an unknown substance.
"Police received a call at approximately 4.15pm yesterday, regarding concern for the welfare of a man and a woman.
"They were taken to Salisbury District Hospital and are being treated for suspected exposure to an unknown substance. They are currently in a critical condition.
"At this stage it is not yet clear if a crime has been committed and a multi-agency response has been co-ordinated.
"Salisbury District Hospital is advising people to still attend routine appointments unless they are contacted.
"There are a number of locations in Salisbury which have been cordoned off in relation to this matter."