British detectives have found the source of the Novichok nerve agent that killed a woman and poisoned her partner in a small bottle in his south-west England home.

Dawn Sturgess, 44, died this month after coming into contact with the nerve agent in Salisbury.

Her partner, 45-year-old Charlie Rowley of Amesbury, a town a few miles from Salisbury, is in a serious condition in the town’s hospital, but has regained consciousness.

“A small bottle was recovered during searches of Charlie Rowley’s house in Amesbury,” Metropolitan Police said in a statement.

“Scientists have now confirmed to us that the substance contained within the bottle is Novichok.”

Ms Sturgess’ death follows Russian double agent Sergei Skripal and his daughter, Yulia, almost dying from the poison applied to their front door in Salisbury in March.

The lethal nerve agent was once produced in the Soviet Union during the Cold War in the 1970s and 1980s.

Prime Minister Theresa May blamed the Russian government for the attack on the Skripals at the time, saying it was “highly likely” Russia was involved, but the Kremlin have denied any involvement.

Police are conducting tests to try to establish if the Novichok that poisoned Ms Sturgess and Mr Rowley is from the same batch that contaminated the Skripals, the statement added.

Mr Rowley will also be questioned about why he had the bottle containing Novichok in his home, police said.

“This is clearly a significant and positive development,” Head of UK Counter Terrorism Policing Assistant Commissioner Neil Basu said.

Mr Basu declined to provide further details about the bottle containing the nerve agent, but police said inquiries were ongoing to establish where the bottle came from and how it came into Mr Rowley’s possession.

More than 100 police officers had been searching for the source of the Novichok in the towns of Amesbury, where Ms Sturgess and Mr Rowley lived, as well as Salisbury, where the Skripals were poisoned.

Mr Basu said cordons would remain in place in some locations to protect the public despite discovering the source of the Novichok.

Ms Sturgess and Mr Rowley both collapsed in his home in Amesbury within hours of each other on June 30. The 44-year-old woman died in hospital on Sunday.

Hours before the couple were poisoned, London police lifted a cordon on a restaurant once frequented by the Skripals, saying there was no public risk.

Police had cordoned off the restaurant after a man in his 30s had collapsed outside the eatery on Thursday UK time.

Police said he was taken to hospital and confirmed there was no risk to his health or the wider public, while emergency personnel wearing white biohazard suits remained inside the cordon at the Zizzi chain restaurant.

An inquest into Ms Sturgess’ death is set to open and adjourn in Salisbury next Thursday.

-with agencies