The UK counter-terrorism police have launched an investigation into what they say is another attack on British citizens with the Russian nerve agent Novichok, the same poison that was used in March against Russian double-agent Sergei Skripal.
Neil Basu, Britain's most senior counter-terrorism officer, told reporters on Wednesday that two British citizens were critically ill in hospital after coming into contact with the poison.
Identified as a couple living in Amesbury, Dawn Sturgess and Charlie Rowley were taken to the hospital on June 30 after collapsing within hours from each other.
"I have received test results from Porton Down [military research centre] which show that the two people have been exposed to the nerve agent Novichok," Basu said.
Basu said he could not confirm whether the victims, a man and a woman, had been to any of the sites that were supposedly decontaminated after the Skripal attack.
Skripal and his daughter, Yulia, were found unconscious outside a shop in Salisbury. British chemical experts concluded that the nerve agent entered their body after they touched a contaminated door handle.
After the Skripal poisoning, police and chemical experts in protective hazmat suits scoured the ancient English cathedral city. Basu said they might return to the area for more research.
He cautioned that there was no intelligence indicating the couple was targeted deliberately.
UK Home Secretary Sajid Javid said he also doubted the attack was premeditated.
The "working theory is currently that this exposure was accidental, rather than a second attack along the lines of that on Sergei and Yulia Skripal in Salisbury," he noted.
British Prime Minister Theresa May's spokesman said the government’s emergency response committee had met to discuss the incident.
Currently, some 100 counter-terrorism officers are said to be working on the case and police have cordoned off at least five different locations the couple had visited in Salisbury and Amesbury.
The locations included the couple's home, a chemist where they had gone to pick up a prescription, a church and a park. Police did not disclose the fifth location.
The counter-terrorism police said they were looking for possible links between the new attack and the Skripal case, which sent ties between Russia and the UK to their lowest in years. London fired several Russian diplomats over claims that Moscow was behind the attack.
Moscow has denied the allegation, saying Novichok only has a Russian name and many countries, including the UK, have researched it for years.