Two British citizens are critically ill after being exposed to Novichok, the same nerve agent that sickened a former Russian spy and his daughter in March, Britain's top counterterrorism officer has said.
Neil Basu told reporters in the southern town of Amesbury late on July 4 that tests conducted by Britain's Porton Down military research center found that the 44-year-old woman and 45-year-old man had been exposed to Novichok.
The pair was hospitalized after being found unconscious on June 30 at a residence in Amesbury, which is just 11 kilometers away from Salisbury, where Russian ex-double agent Sergei Skripal and his daughter Yulia were poisoned in March.
"It's the same nerve agent. Whether we can ever tell if it's the same batch will be up to scientists to determine," Basu said.
"The priority for the investigation team now is to establish how these two people have come into contact with this nerve agent," he said.
Home Secretary Sajid Javid, who will chair a meeting of Britain's emergency response committee on the incident on July 5, said "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 earlier this year."
Paramedics were called to a house in Amesbury on June 30 after the woman, identified by media as Dawn Sturgess, collapsed. They returned later in the day when the man, Charlie Rowley, also fell ill, media reported.
Both were transported to Salisbury District Hospital for treatment, the same hospital that treated the Skripals during their excruciating, weeks-long recovery from exposure to Novichok.
"We are not in a position to say whether the nerve agent was from the same batch that the Skripals were exposed to," Basu said. "The possibility that these two investigations might be linked is clearly a line of inquiry for us."
Basu said it was unclear how the two Amesbury residents came into contact with the nerve agent or whether they had been specifically targeted.
"I don't have any intelligence or evidence that they were targeted in any way," he said. "There is nothing in their background to suggest that at all."
He also said there was no evidence the man and the woman had "recently visited any of the sites that were decontaminated" after the poisoning of the Skripals.
Britain has accused Russia of poisoning the Skripals with Novichok - a nerve agent developed by the Soviet military during the Cold War - in what is the first known use of such a chemical weapon on European soil since World War Two.
Russia has denied any involvement in their poisoning.
The latest incident has eerie similarities to the Skripal case, which began when the former colonel in Russia's military intelligence service and his daughter Yulia were found slumped unconscious on a bench in Salisbury on March 4.
Around 100 counterterrorism officers are still working on that case and police have cordoned off at least five different areas in Salisbury, including a park.
Police on July 4 cordoned off some sites in Amesbury as well, including a residence, a pharmacy, and a Baptist church community center.
A man in Amesbury, Sam Hobson, 29, told AFP he was a friend of the pair and said he saw the man fall ill.
"He was sweating loads, dribbling, and you couldn't speak to him. He was making funny noises and he was rocking backwards and forwards," Hobson said. "It's like he was in another world."
Roy Collins, the secretary of Amesbury Baptist Church, where the couple reportedly attended an event on June 30, told the BBC that no one else from the church had "suffered any ill effects."
"We are all quite puzzled and shocked. Naturally the connection with Salisbury and recent events there mean there is a heightened public interest," Collins told the broadcaster.
The attack on the Skripals prompted the biggest Western expulsion of Russian diplomats since the Cold War as allies in Europe and the United States acted in solidarity with British Prime Minister Theresa May, who contended that Moscow was either responsible for the poisoning or had lost control of the nerve agent.
Russia, which is currently hosting the World Cup soccer tournament, responded with tit-for-tat expulsions of diplomats from Western countries.
Russian officials questioned why Russia would want to attack an aging double-agent who was pardoned and then traded in a 2010 spy swap with Britain.
The exposure of two more people to Novichok -- neither of whom are known to be involved with espionage or to have connections to Russia -- raised fears that more British citizens could be targeted and that there could still be traces of the nerve agent in Amesbury and Salisbury.
"It is a bit of a scare," Amesbury resident John Reid, 84, told AFP.
But England's Chief Medical Officer Sally Davies on July 4 downplayed that risk.
"As the country's chief medical officer, I want to reassure the public that the risk to the general public remains low," she said.