Detectives investigating the poisoning of two people in the United Kingdom believe the source of the nerve agent was a small bottle found in one of the victim's house in Amesbury, Scotland Yard said.
He declined to give further details on the bottle, but police said inquiries were ongoing to establish where the bottle came from and how it came into Rowley's possession.
Sturgess' partner Charlie Rowley, 45, remains in a critical condition but has regained consciousness.
Two people were exposed to the nerve agent Novichok in Amesbury on 30 June.
Dawn Sturgess died after taking Novichok.
The incident occured just miles from where ex-spy Sergei Skripal, and daughter Yulia, were attacked with the substance in Salisbury in March.
A bottle found at Charlie Rowley's Amesbury house was tested by scientists at Porton Down, the Met Police said.
It was taken for tests where scientists confirmed the bottle contained Novichok. Further scientific tests will be carried out to try and establish whether it is from the same batch that contaminated Sergei and Yulia Skripal in March - this remains a main line of inquiry for police.
Authorities have yet to understand how the couple came across the contaminated bottle and how it ended up in their house.
Charles Rowley is now conscious in hospital and police have found a bottle of Novichok at his house.
A vehicle has been seized by the military outside a police station in north Wiltshire.
A police auto was transported from Monkton Park in Chippenham, Wits, while a rapid response vehicle was taken from the Air Ambulance base in Semington, Wilts.
A post-mortem examinaton will be conducted next Tuesday to investigate Ms Sturgess' death.
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