July 9 (UPI) -- Police are opening a murder investigation after Dawn Sturgess died from exposure to a Russian nerve agent eight days after touching it.
Sturgess, 44, and her partner Charlie Rowley, 45, were poisoned eight days ago by the same Soviet-era nerve agent that afflicted former Russian spy Sergei Skripal and his adult daughter, Yulia, in March.
Sturgess is the first person to die after coming in contact with the Russian nerve agent.
Rowley remains in critical condition.
In both poisoning instances, the agent believed to have been used is a Novichok agent, a substance developed by the Soviet Union during the 1970s.
British police are treating the 44-year-old woman's death as murder, the Telegraph reported, referring to it as "the day we hoped would never come."
Sergei and Yulia Skripal have both recovered since a probe opened into their poisoning in March.
The British couple, Sturgess and Rowley, were found on June 30 unconscious at a house in Amesbury, Wiltshire -- about 10 miles from where Skipal and his daughter were poisoned. Tests showed they were exposed after touching the nerve agent with their hands.
British Prime Minister Theresa May said she was "appalled and shocked" by Sturgess' death, and Home Secretary Sajid Javid said he was "determined" to catch the killers.
The Counter-Terrorism Policing Network and about 100 detectives are working on the investigation with Witshire Police, BBC News reported.
"Detectives will continue with their painstaking and meticulous work to gather all the available evidence so that we can understand how two citizens came to be exposed with such a deadly substance that tragically cost Dawn her life," Neil Basu, Britain's top counter-terrorism officer, said.
Officials suspect Sturgess and Crowley became exposed to the nerve agent after handling a contaminated item.
"We are not in a position to say whether the nerve agent was from the same batch that the Skripals were exposed to," Basu said. "The possibility that these two investigations might be linked is clearly a line of inquiry for us."