Two British citizens have been critically sickened by the same nerve agent, Novichok, that was used to poison a former Russian spy and his daughter four months ago, the British authorities announced Wednesday.
The two victims, a man and a woman, both in their 40s, fell ill on Saturday in the southern town of Amesbury, England, after having visited nearby Salisbury, including a spot near where the spy and his daughter were stricken in March, the police said.
The emergence of additional Novichok victims, after four months of meticulous decontamination and public reassurances, presents British authorities with a daunting challenge.
If the nerve agent was left behind by attackers in March, then traces of it may remain in places the authorities did not search, presenting an unpredictable threat to the public. If the agent was deposited more recently, then the poisonings were not an isolated attack.
In either case, a crisis that Britain has struggled to bring under control has now moved into an uncertain new phase.
The victims, identified locally as Charlie Rowley, 45, and Dawn Sturgess, 44, are British citizens, and the police said there was no indication that they would have been targets.
Before they collapsed, the two had spent time in the Queen Elizabeth Gardens in Salisbury, which is a short walk where the former spy and his daughter lost consciousness. Officials cordoned off the area on Wednesday, along with several other places, including a trash bin outside the John Baker House, an assisted-living centre in Salisbury.
A friend who was with Mr. Rowley and Ms. Sturgess on Saturday said that their condition rapidly deteriorated, with symptoms that included pinpoint pupils, seizures, frothing at the mouth and hallucinations.
The police said Wednesday that they did not know whether there was a link between the new case and the poisoning of the former spy, Sergei Skripal, and his daughter, Yulia. Britain has accused the Russian government of being behind the earlier attack, a claim Moscow denies.
“The Counter Terrorism Policing Network is now leading the investigation into this incident,” Neil Basu, an assistant commissioner of the Metropolitan Police who oversees counterterrorism operations, announced on Wednesday evening. About 100 detectives are working on the case, along with members of the local Wiltshire Police.
The two victims were in critical condition at Salisbury District Hospital, the authorities said.
In Salisbury, which has struggled to revive its commercial district after the March attack, many were shocked at the thought of starting over. Ruby Vitorino, who works in a jewellery shop, said that the sense of risk had subsided – until Wednesday’s news.
“I got a message from a friend saying, ‘Salisbury is dead, it was Novichok, Salisbury is dead,’” Ms. Vitorino said. “I don’t think we’ve had time to take in all the implications.”
A new set of spaces would now become the focus, she said. “The places they cleaned up were the places the Skripals were – not the places where the assassins were.”
An exhaustive decontamination effort that began in April focused on nine sites related to the Skripals’ movements on March 4, the day they were stricken. They included Skripal’s house, the pub and restaurant where the two spent time that day, the grassy area where they collapsed, the ambulance and police stations used by emergency medical workers and officers, a car storage facility and the house of a detective who responded to the crime.
The sites being investigated in connection with new poisoning are different ones.
The police said a response team was first summoned at 10:15 a.m. London time Saturday to a home in Amesbury, about 8 miles north of Salisbury. Emergency workers returned at 3:30 p.m.
Sam Hobson, who saw the victims on the day they fell ill, told reporters that Sturgess was in the bathroom when she went into a seizure, foaming at the mouth. A few hours later, when Mr. Rowley collapsed, he was sweating heavily, making noises and rocking back and forth.
“There was no response for me – he didn’t even know I was there,” Mr. Hobson said. “He was in another world, he was hallucinating.”
Investigators initially speculated that the two had suffered from a drug overdose, but after further testing by multiple agencies, including Porton Down, the country’s main laboratory for chemical and biological weapons, they concluded that the cause was Novichok, a Soviet-developed strain of nerve agent.
Mr. Basu acknowledged “a great deal of speculation” over a possible connection to the March poisonings of the Skripals.
“However, I must say that we are not in a position to say whether the nerve agent was from the same batch that the Skripals were exposed to,” he said. “The possibility that these two investigations might be linked is clearly a line of inquiry for us. It is important, however, that the investigation is led by the evidence available and the facts alone and we don’t make any assumptions.”
One theory on Wednesday night was that the victims might have touched contaminated items left behind by the Skripals’ assailant in March. The police have said the attacker most likely applied the Novichok to the handle of Skripal’s front door.
“Assume it was the doorknob – the person who put it there would have a coat and gloves they wouldn’t have wanted to leave the country with, and they may have wanted to hide it somewhere,” said Richard Guthrie, an independent chemical weapons expert and the editor of CBW Events.