POLICE sources have said that there are suggestions former Russian spy Sergei Skripal and his daughter Yulia were poisoned at the his home.

Mr Skripal, 66, and his daughter, 33, remain in a critical, but stable, condition in intensive care after being exposed to a nerve agent in Salisbury.

Tom Tugendhat, chairman of the Foreign Affairs Select Committee, has said all the evidence points to the nerve agent attack being ordered by the Kremlin.

Detective Sergeant Nick Bailey, who rushed to the aid of the pair, has also been struck down by the toxic substance.

READ MORE: Poison attack "brazen and reckless", says Rudd.

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Sergei Skripal

Wiltshire Police temporary Chief Constable Kier Pritchard said the officer was in a "serious, but stable, condition" and had since regained consciousness.

Home Secretary Amber Rudd, who yesterday called the attack "brazen", visited the scene and spoke to investigators this morning.

She will make a private visit to Salisbury District Hospital, where the three are being treated. It is unclear whether she will be able to visit any of the victims.

Police said a total of 21 people had been seen for medical treatment in the aftermath of the incident.

The figure includes members of the public and emergency staff, some of whom have had blood tests as well as receiving support and advice.

It is feared that Mr Skripal - who was convicted in his home country for selling secrets to MI6 - was singled out for a state-sponsored assassination plot.

DS Bailey, meanwhile, was praised as "well liked, well loved, a massively dedicated officer" as he continued to recover from the attack.

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In a statement, Lorna Wilkinson, director of nursing at Salisbury NHS Foundation Trust, said: "Following the incident in Salisbury on Sunday, we are treating three inpatients at Salisbury District Hospital.

"A man in his 60s and a women in her 30s remain in a critical, but stable condition in intensive care after being exposed to a nerve agent. The police officer, who was also part of the initial response, is conscious in a serious but stable condition."

"In addition to the three inpatients receiving treatment, in line with Public Health England guidance which asked anyone who was in the area and concerned to come forward if feeling unwell, we have seen and assessed a number of people who did not require further treatment."