Police say they have found the source of the latest Novichok poisonings.
A small bottle discovered at victim Charlie Rowley's Amesbury house on Wednesday has been found to contain the deadly substance.
It was rushed to the Defence laboratory at Porton Down for tests, which revealed that the vial does indeed contain Novichok, reports Daily Mail.
The latest poisoning claimed the life of 44-year-old Dawn Sturgess while Mr Rowley remains in hospital.
The discovery at the Muggleton Road address is a major breakthrough for British counter terrorism forces who have so far been unable to trace the source of the deadly substance.
Further tests are being done on the contents of the bottle to discover whether it is from the same batch used on former-spy Sergei Skripal and his daughter Yulia in March.
The bottle may prove to be the missing link in explaining how Russian operatives poisoned the Skripals earlier this year.
Britain has invited independent technical experts from the international chemical weapons watchdog to travel to the UK early next week to independently confirm the identity of the nerve agent, the British Foreign Office also confirmed today.
In a statement today, Scotland Yard said: "On Wednesday, 11 July, a small bottle was recovered during searches of Charlie Rowley's house in Amesbury. It was taken to the Defence, Science and Technology Laboratory at Porton Down, Wiltshire, for tests.
"Following those tests, scientists have now confirmed to us that the substance contained within the bottle is 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 enquiry for police.
"Inquiries are under way to establish where the bottle came from and how it came to be in Charlie's house."
Assistant Commissioner Neil Basu, Head of UK Counter Terrorism Policing, said: "This is clearly a significant and positive development. However, we cannot guarantee that there isn't any more of the substance left and cordons will remain in place for some considerable time. This is to allow thorough searches to continue as a precautionary measure for public safety and to assist the investigation team.
"I also appreciate there is a lot of interest in this; however, we are not in a position to disclose any further details regarding the bottle at this stage.
"The safety of the public and our officers remains paramount and we are continuing to work closely with Wiltshire Police, scientists, health experts from Public Health England and other partners."
Chief Constable Kier Pritchard revealed from next week the force would be drafting in private security staff to man cordons in Salisbury and Amesbury, both Wilts.
The police chief said this move will "free up" officers who have been stood guard at five sites across the cathedral city and nearby Amesbury.
Despite investigators believing they have found the source of the Novichok, the chief constable said people should still avoid picking things up from the ground while in Salisbury.
Chief Constable Pritchard said: "Today's update from the investigation team is both significant and encouraging.
"I hope that it will further reassure our communities in both Amesbury and Salisbury that the investigation, although complex, is meticulous.
"We continue to support colleagues from the Counter Terrorism Policing Network to progress the inquiry as swiftly and safely as possible.
"Despite this latest development from the investigation team, the guidance from Public Health England around picking up foreign objects hasn't changed.
"It's a highly precautionary measure and the overall risk to the public is low but their advice is simple - 'If you didn't drop it, don't pick it up'."
The pair fell ill at Mr Rowley's home in Amesbury - eight miles from Salisbury - on June 30, with anti-terror police launching a massive operation to find the source of the contaminant, which was believed to be inside a container.
The Novichok saga began in March when Sergei and Yulia Skripal mysteriously fell ill on a park bench in Salisbury. They were found to have been poisoned with Novichok, a lethal nerve agent produced in the Soviet Union during the Cold War.
Prime Minister Theresa May blamed the Russian government for the attack, which the Kremlin vehemently denied.
The Skripals survived and have been released from a hospital, but are in a secret protected location.
The case led the United States and other countries to expel a large number of Russian diplomats.
Staff at Salisbury District Hospital said Mr Rowley has made a "a small but significant improvement" and has regained consciousness but still needs round-the-clock care.
Tributes have been paid to mother-of-three Ms Sturgess, with her family saying: "Dawn's death has been devastating for us. Dawn will always be remembered by us as a gentle soul who was generous to a fault."
While the advice from Public Health England is that the risk to the public is low, Chief Medical Officer Dame Sally Davies has warned everyone in the area not to pick up "any foreign object which could contain liquid or gel, in the interests of their own safety".
Central to the investigation are John Baker House, the supported-living accommodation where Ms Sturgess lived, Mr Rowley's home in Amesbury, and Salisbury's Queen Elizabeth Gardens, which remains cordoned off.
The Government pledged over £5million (NZ$9.7million) to support businesses and meet costs in Salisbury and Amesbury after the area was rocked by a second nerve agent poisoning.
The large sum follows a £2.5million (NZ$4.8million) boost the government initially pledged to support the community in Salisbury following the Novichok attack on former Russian double agent Sergei Skripal and his daughter Yulia.
The £5.3 million (NZ$10.3million), awarded after Dawn Sturgess, 44, and Charlie Rowley, 45, became contaminated by traces of the deadly nerve agent, will support Salisbury and Amesbury, both Wilts, through another investigation and clean-up.