Investigators have been summoned for emergency talks on the crisis in Salisbury, where the fallout from a suspected nerve agent attack continues to widen.
Home Secretary Amber Rudd will chair a meeting of the Government’s Cobra committee at 3pm on Saturday to receive updates on the police case, Downing Street said.
Detective Sergeant Nick Bailey, who was part of the initial response by authorities, is also in a serious condition.
Police turned their attention on Friday to the cemetery where the 66-year-old Russian’s wife and son were laid to rest.
Officers in hazmat suits were seen placing a blue forensic tent over his son’s memorial stone before appearing to stuff items in several yellow barrels.
A short distance away, a convoy of military vehicles rolled into the car park at Salisbury District Hospital to recover a police car.
Around 180 troops, including Royal Marines, RAF Regiment troops and chemical warfare specialists, are understood to have been deployed after Scotland Yard requested specialist help.
Suspicion is mounting that Russia carried out the attempt on their lives as an act of revenge against the former intelligence officer, who was convicted in 2006 of selling state secrets to MI6.
He was later released as part of a spy swap with the US.
The Kremlin denies responsibility and British ministers have urged caution over apportioning blame until the facts become clear.
“Some big questions arise as to how do you stand up to a clandestine and sinister attack deliberately done to play havoc in our society?”
Mrs Rudd had earlier visited Salisbury and the hospital where DS Bailey is receiving treatment.
Lord Blair, a former Met Commissioner, suggested on the BBC’s Today programme the seriously ill detective had visited Mr Skripal’s home.
He said: “There obviously are some indications the officer, and I’m very sorry that he has been injured, has actually been to the house, whereas there was a doctor who looked after the patients in the open who hasn’t been affected at all.
“So there may be some clues floating around in here.”
Police said 21 people had been seen for medical treatment since 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.
The attack is being treated as attempted murder.