Independent investigators have confirmed the toxic chemical that killed Dawn Sturgess in Amesbury was the same nerve agent as that which poisoned Sergei and Yulia Skripal three months earlier.
The Organisation for the Prohibition of Chemical Weapons (OCPW) said its team had confirmed the findings of the UK, which concluded in July that the substance used was Novichok.
Ms Sturgess and her partner Charlie Rowley fell ill at his home in Amesbury, near Salisbury, on June 30.
Ms Sturgess, a mother-of-three, died in hospital eight days later having never regained consciousness.
It is believed they were exposed to a military grade nerve agent from a perfume bottle discarded by those responsible for the attack on former Russian double agent Sergei Skripal and his daughter Yulia in March, which also saw Wiltshire police officer Detective Sergeant Nick Bailey caught up in the attack.
The OPCW on Tuesday evening said: "The results of the analysis by the OPCW designated laboratories of environmental and biomedical samples collected by the OPCW team confirm the findings of the United Kingdom relating to the identity of the toxic chemical that intoxicated two individuals in Amesbury and resulted in one fatality.
"The toxic chemical compound displays the same toxic properties of a nerve agent.
"It is also the same toxic chemical that was found in the biomedical and environmental samples relating to the poisoning of Mr Sergei Skripal, Ms Yulia Skripal, and Mr Nicholas Bailey on March 4 in Salisbury."
The OPCW said: "The team collected a sample of the contents of a small bottle that the police seized as a suspect item from the house of Charles Rowley in Amesbury.
The Metropolitan Police's counter-terror head Neil Basu said on July 4: "This evening we have received test results from Porton Down that show the two people have been exposed to the nerve agent Novichok."