The nerve agent Novichok could remain active for 50 years if kept in a sealed container, Britain's top counterterrorism police officer said Wednesday, adding that he cannot yet "guarantee" there are no traces of the lethal poison in southwestern England.
"Dawn will always be remembered by us as a gentle soul who was generous to a fault", they said in a statement released by London's Metropolitan Police.
Novichok was invented by the Soviet Union and is one of the most toxic substances known to man, it blocks instructions from nerves to muscles and causes huge pain and death.
She is believed to have touched an item contaminated with Novichok, the poison used in a failed attempt to assassinate former Russian spy Sergei Skripal, 67, and his daughter Yulia, 33, in March.
"The public health advice remains the same, with the current risk to the public remaining low, but anyone with concerns can call the dedicated helpline that has been set up in Wiltshire on 0800 092 0410".
The UK government has blamed Russian Federation for the incident, but the authorities in the Motherland deny any involvement.
"We have seen a small but significant improvement in the condition of Charlie Rowley", said Lorna Wilkinson, Director of Nursing at Salisbury District Hospital.
Novichok poison victim Charlie Rowley regained consciousness on Tuesday and is now in a critical but stable condition, Salisbury District Hospital announced.
The wide investigation is now a homicide inquiry.
Sturgess died Sunday, leaving behind her three children, police said.
Ms Sturgess lived in Salisbury, and the couple had been in the city before going to Mr Rowley's flat in nearby Amesbury on Friday 29 June. 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.
A Kremlin spokesman on Monday (Tuesday NZT) expressed condolences over Sturgess' death.
He warned the investigation into the latest poisonings would take months. Peskov added that such attacks present a danger not only inside the United Kingdom, but also in Europe as a whole. He said, "It's Britain's problem and the problem of how interested Britain is in a real investigation".