Image copyright Facebook Image caption The couple, believed to be Dawn Sturgess and Charlie Rowley, spent Friday in Salisbury

On Saturday, paramedics were called twice to a house in Muggleton Road in Amesbury - first at 11:00 BST after Ms Sturgess collapsed, then later the same day, after Mr Rowley also fell ill.

Wiltshire Police said it was initially thought the two patients had been using heroin or crack cocaine from a contaminated batch of drugs. The pair remain in critical condition in Salisbury District Hospital, the same hospital where former double agent Sergei Skripal and his daughter were treated after they were exposed to Novichok, a military-grade nerve agent. Police officers guard outside a branch of Boots pharmacy, which has been cordoned off after two people were hospitalised and police declared a 'major incident', in Amesbury Thomson Reuters

AMESBURY, England (Reuters) - Britain's counter-terrorism chief said on Wednesday that two people who are critically ill in hospital in Wiltshire were exposed to the Novichok nerve agent, the same toxin that was used in an attack on ex-Russian spy Sergei Skripal. “As Wiltshire Police have stated, they are keeping an open mind as to the circumstances surrounding the incident.”

Police in Wiltshire, where Russian ex-double agent Sergei Skripal and his daughter Yulia were poisoned with a nerve agent in March, took the rare step of declaring a major incident after a man and a woman were found unconscious on Saturday in Amesbury. More: Nerve agent leaves couple in critical condition near site of UK spy attack

Related: Former Russian spy Sergei Skripal discharged from hospital after poisoning

Kremlin spokesman Dmitry Peskov said Thursday that Russia had nothing to do with either incident. He said “the British side has not presented any evidence of Russia’s involvement in this, besides unfounded accusations.”

Authorities believe Rowley and Sturgess, British nationals with no known links to Russia, were not deliberately targeted. UK Security Minister Ben Wallace said Thursday in a BBC interview that the British government would find out who was responsible for the latest nerve agent poisonings and what exactly happened in Wiltshire “no matter how long it takes.”

Rowley and Sturgess live in Amesbury, a town of fewer than 10,000 people about 20 minutes’ drive from Salisbury where the Skripals were poisoned. “I do want to reassure the public, however, that there is no evidence that either the man or woman recently visited any of the sites that were decontaminated following the attempted murders of Sergei and Yulia Skripal,” he said. Russian spy found unconscious in English park sparks intrigue

Public health officials said the risk to the public is low, but advised people who had visited five locations in Amesbury and Salisbury between Friday night and Saturday evening including a park, a drugstore and a church to wash the clothing they were wearing and wipe personal items such as phones with cleansing or baby wipes.
Police determine two British nationals found unconscious at a property in Amesbury, Wiltshire, on Saturday were poisoned using Novichok nerve agent of the same kind used in the poisoning of Sergei and Yulia Skripal in Salisbury, seven miles from Amesbury, almost four months ago.