Authorities have broadened their investigation into the nerve agent poisoning of an English couple, seizing a vehicle in a third community in southwestern England.
A woman who died after being poisoned with a nerve agent that also struck a former Russian spy in March must have handled a contaminated item, and tracking it down is key to police investigations, Britain's top counter-terrorism officer said.
It killed Sturgess, 44, who died on Sunday evening.
He said scientists would continue to establish if the nerve agents are from the same batch, but that the Defence, Science and Technology Laboratory at Porton Down are "already crystal clear" that both are Novichok.
Mr Skripal, 67, and his 33-year-old daughter were left in a critical condition after they were found slumped on a bench in Salisbury city centre on 4 March.
On Tuesday morning, a white Audi was removed from Swindon, about 40 miles from Salisbury, as part of investigations into the novichok poisonings.
It was unclear if Williamson was referring to the attack on the Skripals or a new attack.
Staff at Salisbury District Hospital said Charlie has made a "a small but significant improvement" and has regained consciousness but still needs round-the-clock care.
Asked about whether his brother is aware of Ms Sturgess's death, Matthew said Charlie was "very upset".
Britain's Assistant Police Commissioner for Specialist Operations, Neil Basu, delivers a statement to the media regarding the poisoning of two people in Salisbury, at New Scotland Yard in London, Britain, July 9, 2018.
Mr Basu also said that the "brutal reality" is that he can not say with certainty that there are no traces of nerve agent left anywhere in Wiltshire.
The British government has accused Russian Federation of being behind the attack on Mr Skripal, who settled in the United Kingdom after a spy swap. In May, the UK's national security adviser Sir Mark Sedwill said authorities did "not yet" know who was responsible for the Skripal death, and no updates have been offered since.
He said no one else in the Amesbury and Salisbury region, where the couple lived in southwestern England, has shown any sign of Novichok poisoning.
Five site are now cordoned off in Amesbury and Salisbury after the poisoning of Charlie Rowley and Dawn Sturgess. The search is focused on their homes and a park in Salisbury. Moscow has strongly denied any responsibility and hit back by expelling a spate of western diplomats. Peskov added that such attacks present a danger not only inside the United Kingdom, but also in Europe as a whole.