Traces of the Novichok nerve agent have been found in the blood of a second police officer following the chemical attack in Salisbury last year.
Wiltshire Police say their officer, who has chosen not to be named, was treated quickly and was able to return to work shortly afterwards.
It's said they were involved in the response to the poisoning of Sergei and Yulia Skripal and they displayed signs at the time, that suggested they had been exposed to a "very small amount" of Novichok.
"Forensic examination of the officer's blood sample that was taken in March 2018 has since been carried out by scientists at Dstl on behalf of the investigation team," Wiltshire Police said in a statement.
"The forensic test - which uses a different method to that used to assess the clinical effects of nerve agent poisoning - has now given detectives confirmation that traces of Novichok were in the blood sample.
"These forensic tests were carried out as part of what remains an ongoing investigation, which has been unprecedented in its complexity and scale and has involved thousands of exhibits.
"Officers continue to work closely with scientists and experts to meticulously and methodically review and examine the evidence available to us."
Wiltshire Police say their officer has been told and continues to receive support.
They are now the fourth person to be confirmed through forensic testing as a victim of the initial Salisbury attack.
The higher levels of exposure to Novichok suffered by the Skripals and Detective Sergeant Nick Bailey led to them falling critically or seriously ill.
Dawn Sturgess and Charlie Rowley also suffered high levels of exposure to Novichok following the incident in Amesbury in June 2018. Tragically, Dawn died some days later, whilst Charlie also became critically ill.
In their statement Wiltshire Police added detectives from the Counter Terrorism Policing network have also contacted "a small number" of other people who's blood samples were taken at the time, to ask permission to carry out further forensic tests.
They say there is no need for anyone else, who has not been contacted, to take any action.
"Furthermore, public health experts have confirmed that there is no change to the overall public health risk, which remains low," Wiltshire Police say.
"However, should anyone have any concerns, then they can contact the NHS by calling 111."
Two men known as 'Alexander Petrov' and 'Ruslan Boshirov' are wanted by UK police after the Crown Prosecution Service authorised charges against the pair, linked to the attack on Sergei and Yulia Skripal and Detective Sergeant Nick Bailey.
In September last year the pair appeared on Russian State television and denied any involvement in the poisoning, insisting instead that they were in Salisbury to see the Cathedral.