UK police are believed to have identified the suspected perpetrators of the Novichok attack on Russian former spy Sergei Skripal and his daughter, Yulia.
Officers think several Russians were involved in the attempted murder of the former double agent and his daughter in Salisbury and are looking for more than one suspect.
"Investigators believe they have identified the suspected perpetrators of the Novichok attack through CCTV and have cross-checked this with records of people who entered the country around that time. They are sure they (the suspects) are Russian," a source with knowledge of the investigation told the Press Association.
The news comes as an inquest is due to open on Thursday for Dawn Sturgess, who died earlier this month, eight days after apparently coming into contact with Novichok from the same batch used in the attempted murder of the Skripals in March.
Her partner Charlie Rowley, was left fighting for his life after also being contaminated by the chemical weapon.
It is understood Ms Sturgess was exposed to at least 10 times the amount of nerve agent the Skripals came into contact with.
Dawn Sturgess and Charlie Rowley, were found unconscious after being poisoned with Novichok. Ms Sturgess has since died in hospital. Source: Facebook
Investigators are working to the theory that the substance was in a discarded perfume bottle found by the couple in a park or somewhere in Salisbury city centre and Ms Sturgess sprayed Novichok straight on to her skin.
The Metropolitan Police, who are leading the investigation, declined to comment.
On Wednesday, a fingertip search of Queen Elizabeth Gardens in Salisbury was carried out.
The park and other locations in Salisbury and nearby Amesbury were cordoned off last month after the exposure of the couple to the nerve agent.
Last week counter-terrorism detectives revealed they had found a small bottle containing Novichok at Mr Rowley's home in Amesbury.
