A woman who was exposed to a military-grade nerve agent in the United Kingdom last month has died, authorities said Sunday.
London's Metropolitan Police Department identified the woman as 44-year-old Dawn Sturgess of Durrington. Authorities have launched a murder inquiry into her death, police said.
A 45-year-old man who was also exposed to the nerve agent Novichok remains hospitalized in critical condition, police said.
"This terrible news has only served to strengthen our resolve to identify and bring to justice the person or persons responsible for what I can only describe as an outrageous, reckless and barbaric act," Neil Basu, the head of U.K. counterterrorism policing, said in a statement.
Basu said that Sturgess leaves behind three children, and offered thoughts and prayers for the woman's family.
"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," he said.
Sturgess was found by emergency medical workers after she collapsed at a residence in Amesbury and was subsequently taken to the hospital. Hours later, emergency workers responded to the same address after the 45-year-old man became ill, police said.
Both were determined to have been exposed to the nerve agent after touching a contaminated item with their hands, police said.
Authorities later determined that both people had been exposed to Novichok, a military-grade nerve agent produced by the Soviet Union decades ago.
The poisonings came months after a former Russian double agent, Sergei Skripal, and his daughter, Yulia Skripal, were found on a park bench after being exposed to the nerve agent. Both survived the exposure and have since been discharged from the hospital.
The U.K. and other Western officials have blamed Russia for carrying out the attack on the Skripals — a charge that Moscow has denied. A number of Western countries expelled dozens of Russian diplomats in response to the poisonings.
There is no evidence that Sturgess and the other victim visited any of the sites that had been decontaminated after the Skripals' poisoning, police said, adding that they could not say whether the nerve agent came from the same batch as the one the Skripals came in contact with.
Detectives are still working to determine the source of the contamination.