Amesbury incident latest: Met Police counterterror unit brought into suspected Wiltshire poisoning

Police say they are 'keeping an open mind' on the circumstances

Counterterror police are working on the investigation into a suspected poisoning in Wiltshire.

A major incident was declared after two people, who The Independent understands are a British couple, were found unconscious at a home in Amesbury.

They remain in a critical condition in Salisbury District Hospital, while the unknown substance used is reportedly undergoing testing at the nearby Porton Down military research facility.

Theresa May attended a meeting of the government's Cobra emergencies committee on Wednesday morning to discuss the incident.

A Downing Street spokesperson said it was "understandably being treated with the utmost seriousness" and the Prime Minister would be kept updated.

A spokesperson for the Metropolitan Police said: "As you would expect, given the recent events in Salisbury, officers from the counterterrorism network are working jointly with colleagues from Wiltshire Police regarding the incident in Amesbury.

"As Wiltshire Police have stated, they are keeping an open mind as to the circumstances surrounding the incident and will update the public as soon and as regularly as possible."

There has been no indication that the incident is terror-related, and counterterror police also led the investigation into the Salisbury nerve agent attack because of their expertise and capacity.

The Metropolitan Police has specialist chemical, biological, radiological and nuclear (CBRN) units that can be deployed anywhere in the UK.

Former Russian double agent Sergei Skripal and his daughter were poisoned with novichok in Salisbury, less than 10 miles from Amesbury, on 4 March.

They were initially in a critical condition but have since been discharged from hospital and are recovering in secret locations amid a continuing police investigation to find the culprit.

The British government has held Russia culpable for the attack, as novichoks were initially developed by the Soviet Union and the Kremlin did not explain how it might have lost control of the weapon.

Police have not confirmed any link between the two incidents and the investigation is ongoing.

A source told The Independent that there was no obvious connection with the Skripals. The couple are British and have no known link to espionage.

Officials wearing “green suits” have been seen at the Amesbury flat where the two patients, an unnamed couple in their 40s, were found unconscious after being exposed to an unknown substance on Saturday.

A police cordon at Queen Elizabeth Gardens in Salisbury, Wiltshire, one of the sites cordoned off after a major incident was declared (PA)

Wiltshire Police said they were initially feared to have used contaminated heroin or crack cocaine but further testing is ongoing and investigators are keeping “an open mind”.

The flat where the couple were found unconscious, in Muggleton Road, Amesbury, is one of several sites in the town and nearby Salisbury that have been cordoned off by police.

Nearby resident Chloe Edwards described seeing police cars, fire engines and people in “green suits” on Saturday night.

"We were just eating our dinner and all these emergency vehicles turned up,” the 17-year-old student said.

"They were putting on these green suits and we thought it was the gas as our electricity was turned off as well."

Ms Edwards said the vehicles arrived at about 7pm and she and her family were told to stay inside their home until about 10pm.

"We wanted to know what happened and with the Russian attack happening not long ago, and we just assumed the worst," she added.

"I am not sure how long they were in there but we couldn't get out of the house for two-and-a-half hours."

(AFP/Getty Images (AFP/Getty Images)

She added that firefighters had connected a hosepipe to the water mains – a procedure that is commonly used for decontamination.

A specialist "decontamination shower" was taken to the scene by Dorset and Wiltshire Fire and Rescue Service on Saturday, but a crew from Swindon later tweeted that “thankfully the incident wasn't serious and our decontamination shower wasn't required”. The tweet has since been deleted.

It is believed that one of the last places the couple were seen in public was a family fun day at Amesbury Baptist Church, which has since been cordoned off, on Saturday afternoon.

Roy Collins, church secretary, said: "Last weekend we held a community fundraiser and we understand this may well be the last event this couple went to in public.

“We are all quite puzzled and shocked - naturally the connection with Salisbury and recent events there mean there is a heightened public interest.

”We are praying for the couple, one of our members knows them and clearly there are concerns for them and any others in the community.

“They are not church members or regulars.”

Mr Collins said around 200 people attended the event, including many families and children, but “nobody else has suffered any ill effects”.

Public Health England said there was not believed to be a significant health risk to the wider public.

Additional reporting by PA