Updated: 06/03/18 : 08:23:57Printable Version
Police are trying to identify a substance which caused a former Russian agent convicted of spying for Britain to collapse in Salisbury, Wiltshire.
Sergei Skripal, 66 - who was granted refuge in the UK in 2010 as part of a "spy swap" - and a 33-year-old woman are critically ill in hospital.
Meanwhile police have closed the city's Zizzi restaurant "as a precaution".
The pair were found slumped unconscious on a bench at the Maltings shopping centre on Sunday.
Wiltshire Police said the pair had no visible injuries and officers were investigating whether a crime had been committed.
Temporary Assistant Chief Constable Craig Holden said: "They are currently being treated for suspected exposure to an unknown substance.
"The focus is trying to establish what has caused these people to become critically ill.
"We are working with partners to prioritise this diagnosis and ensure that they receive the most appropriate and timely treatment."
He said the police's "major incident" response was not a counter-terrorism investigation.
But he said multiple agencies were involved and police were keeping an "open mind".
Col Skripal, who is a retired Russian military intelligence officer, was jailed for 13 years by Russia in 2006.
He was convicted of passing the identities of Russian intelligence agents working undercover in Europe to the UK's Secret Intelligence Service, MI6.