LONDON (AFP) - British police on Monday (July 9) said they could not rule out further contaminations after a 44-year-old mother of three died in southwest England following exposure to the nerve agent Novichok.
"I simply cannot offer any guarantees," assistant commissioner Neil Basu, the head of Britain's counter-terror police, which is leading the investigation, told reporters.
While Mr Basu emphasised that public health authorities had said the risk was "low", he added: "I do, however, recognise there will still be people in the local area with concerns."
Ms Dawn Sturgess died on Sunday (July 8) and her 45-year-old partner Charlie Rowley is still critically ill in hospital after the two collapsed at Mr Rowley's home near Salisbury on Saturday (July 7).
Police have now launched a murder investigation.
Salisbury is where former Russian double agent Sergei Skripal and his daughter Yulia were poisoned with the same Soviet-made toxin four months ago before recovering.
Britain blamed Russia for the poisoning - a charge strongly denied by Moscow which has challenged British authorities to show the evidence.
Mr Basu said the two "must have got a high dose" and police were seeking a "container" they are believed to have handled.
He said public health advice was "not to pick up any strange items such as needles, syringes or unusual containers".
Mr Basu also said that 21 people had presented themselves to medical authorities with "concerns" since last week but had been screened and given the all-clear.
Mr Basu said Ms Sturgess left behind two sons, aged 19 and 23, and an 11-year-old daughter.
He said the "main line of inquiry" was a connection between the Skripal poisoning and the case of Mr Rowley and Ms Sturgess but said scientists had not been able to determine whether the nerve agent came from the same batch.
"We will do everything we possibly can to bring those responsible to justice," he said, calling the use of Novichok an "outrageous, reckless and barbaric act".