The head of UK Counter Terrorism policing, Assistant Commissioner Neil Basu, said Sturgess, a mother of three, died as the result of "an outrageous, reckless and barbaric act".
According to police, Dawn Sturgess, 44, and a 45-year-old man became sick on June 30 in Amesbury, England. Hours later, emergency workers responded to the same address after the 45-year-old man had fallen ill, police said.
A woman who was exposed to the nerve agent Novichok in southern England has died, police announced Sunday.
The Skripal attack took place in the city of Salisbury, just a few kilometres away from the site of the Amesbury poisoning incident.
"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.
The March attack on the Skripals prompted the biggest Western expulsion of Russian diplomats since the Cold War as allies sided with Britain's view that Moscow was either responsible or had lost control of the nerve agent.
Russian Federation denied any involvement in the Skripal incident, and suggested that British police had orchestrated it to stoke anti-Russia sentiments.
British PM Theresa May has expressed outrage over the death of Dawn Sturgess.
Dozens of detectives are working on the investigation, which is being led by the Counter Terrorism Policing Network, as well as officers from the Wiltshire Police Department.
Skripal and his daughter were both released from the hospital this spring.
The British couple were believed to have become exposed to Novichok by handling a "contaminated item", with speculation that it could have been the container used to administer the nerve agent to the Skripals.
"Police and security officials are working urgently to establish the facts of this incident, which is now being investigated as a murder", the statement read.
Police are still trying to piece together how Ms Sturgess and Mr Rowley came into contact with Novichok.
Dawn Sturgess died after exposure to a nerve agent in southeast England.
Police say the nerve agent that sickened Rowley and Sturgess was the same type that nearly killed the Skripals, but scientists haven't been able to tell whether it was from the same batch.
John Glen, the MP for the region, said the new poisoning has threatened an economic rebound from the slowdown caused by the attack on the Skripals.