SALISBURY, ENGLAND - MARCH 07:  A police tent is seen behind a cordon outside The Maltings shopping centre where a man and a woman were found critically ill on a bench on March 4 and taken to hospital sparking a major incident, on March 7, 2018 in Wiltshire, England. Sergei Skripal, who was granted refuge in the UK following a 'spy swap' between the US and Russia in 2010, and his daughter remain critically ill after being exposed to an 'unknown substance'.  (Photo by Matt Cardy/Getty Images)
Police: Russian spy was deliberately poisoned
02:28 - Source: CNN
London CNN  — 

Around 180 British troops have been deployed to the English city of Salisbury to aid in the investigation of a nerve agent attack on a former Russian double agent and his daughter.

Personnel from the Royal Air Force, British Army and Royal Navy were among those sent to Salisbury on Friday, a Ministry of Defence spokesman told CNN.

London’s Metropolitan Police tweeted that the public should not be alarmed and the public health advice remained the same. It explained that the counterterrorism division had requested assistance from the military to “remove a number of vehicles and objects from the scene.”

A split image showing former Russian spy Sergei Skripal and his daughter, Yulia Skripal.

Former Russian spy Sergei Skripal, 66, and his daughter Yulia, 33, were still hospitalized in “very serious condition” after being poisoned earlier this week, UK Home Secretary Amber Rudd said as she visited Salisbury on Friday.

The pair – believed by authorities to have been deliberately targeted – were found slumped on a bench near a shopping center on Sunday afternoon.

Rudd visited several of the sites cordoned off by investigators before heading to Salisbury District Hospital.

Detective Sgt. Nick Bailey, a policeman who also fell ill, is in serious condition, but is “conversing and engaging” with visitors, Rudd added.

Authorities earlier revealed 21 people had received medical attention in the aftermath of the incident, but only three people were still being treated Friday.

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Military personnel, pictured arriving at Salisbury District Hospital on Friday, were deployed to help remove potentially contaminated vehicles and help gather evidence.

Kier Pritchard, temporary chief constable of Wiltshire police, which covers Salisbury, told Britain’s Sky News on Thursday that “multiple” police officers and members of the public had been assessed by medics: “A number of those had been through the hospital treatment process, there have been blood tests and they’re having treatment in terms of support and advice.”

Identifying the source of the nerve agent continues to be central to the probe but so far, Rudd has refused to name any potential culprits.