The British woman who was recently poisoned by the same nerve agent that almost killed a Russian spy and his daughter earlier this year has died, police said Sunday.

Dawn Sturgess, 44, died more than a week after authorities believe she was exposed to Novichok — the agent that poisoned Sergei Skripal and Yulia Skripal in March.

Charlie Rowley, a 45-year-old man who was also exposed to the agent, remains in critical condition, according to London’s Metropolitan Police Service

“This is shocking and tragic news,” Neil Basu, head of U.K. Counter Terrorism policing, said. “Dawn leaves behind her family, including three children, and our thoughts and prayers are with them at this extremely difficult time.” 

The Metropolitan Police added that its detectives had launched a murder inquiry.

Police said Sturgess became ill at a home in Amesbury at around 10 a.m. on June 30 and was hospitalized. Roughly five hours later, Rowley also became ill.

Authorities confirmed on Wednesday that both Sturgess and Rowley were exposed to Novichok. Police suspect the couple were exposed through a contaminated item left over from the attack on the Skripals, which Britain blames on Russia. Russia has denied the allegation.

Amesbury is approximately eight miles from Salisbury, where the Skripals were poisoned. Police have cordoned off multiple sites in both cities and forensic searches were due to be carried out at the home where Sturgess and Rowley collapsed, and other sites the couple visited before they were sickened.

Experts say just a few milligrams of the odorless Novichok liquid — the weight of a snowflake — is enough to kill a person within minutes. But finding residue before it poisons unwitting victims is the problem.

The Associated Press contributed to this report.

Nicole Darrah covers breaking and trending news for Follow her on Twitter @nicoledarrah.