Police suspect Rowley and Sturgess handled a discarded item from the first attack, though they have not determined for certain that the two cases are linked. The investigation is being led by detectives from the Counter-Terrorism Policing Network and about 100 detectives are working on the case alongside Wiltshire Police. "Dawn leaves behind her family, including three children, and our thoughts and prayers are with them at this extremely hard time", Assistant Commissioner Neil Basu, the head of UK Counter Terrorism Policing said.
Prime Minister Theresa May said she is "appalled and shocked", and sent her "thoughts and condolences" to the family.
Per CNN, authorities now believe that Sturgess and Rowley came into contact with a contaminated item via their hands, but now lack the ability to determine whether the poison is from the same batch that the Skripals ingested. But we're determined to find out how Dawn and her partner, Charlie Rowley, came into contact with such a deadly substance and will do everything we can to bring those responsible to justice.
"As part of this, detectives had identified a red Ford Transit van that Charlie travelled in as a passenger on Saturday, prior to falling ill".
Russian Federation has denied any involvement in the poisoning of Skripal and his daughter Yulia with a nerve agent that was developed in the Soviet Union.
In addition to Sturgess and Rowley, 21 people have been examined by health experts over concerns they could have been exposed to the Novichok - eight police officers and staff, nine health care workers, one paramedic and three members of the public.
"I simply can not offer any guarantees", he said, adding that public health authorities said the risk was low.
The poisoning of Sergei Skripal and his daughter triggered an worldwide outcry against Russian Federation, despite the Kremlin's denials that it was involved in the attack against the ex-double agent, while offering conflicting explanations about how they fell ill in Salisbury.
The Skripals both survived despite extended stays in hospital.
Although the United Kingdom has not officially blamed Russia for the latest poisoning, Russian officials have already denied any Kremlin involvement.
Yulia Skripal, who was poisoned in Salisbury along with her father, Russian spy Sergei Skripal, speaks to media representatives in London, on May 23, 2018.
Assistant Commissioner Neil Basu, the head of Britain's counter-terror police, said Sturgess' death was "shocking and tragic news".