AMESBURY, England >> For the second time in four months, two people lie critically ill in England’s Salisbury District Hospital after being exposed to a military-grade nerve agent developed in the Soviet Union, British police confirmed late today.

The country’s chief counterterrorism police officer said tests at Britain’s defense laboratory had confirmed what many residents feared — a man and woman in their 40s had been poisoned with the same toxin that almost killed a former Russian spy and his daughter.

“We can confirm that the man and woman have been exposed to the nerve agent Novichok, which has been identified as the same nerve agent that contaminated both Yulia and Sergei Skripal,” said Assistant Commissioner Neil Basu of London’s Metropolitan Police.

Local police declared the case a “major incident” today, four days after the man and woman were found collapsed at a residential building in Amesbury, eight miles (13 kilometers) from Salisbury, where the Skripals were poisoned.

Basu said it was not clear whether there was a link between the two cases, and whether the nerve agent came from the same batch that left the Skripals fighting for their lives.

“The possibility that these two investigations might be linked is clearly a line of enquiry for us,” he said, amid speculation that the victims could have been sickened by residue from the poison used on the Skripals.

Basu said it was unclear whether the two were targeted, but there was “nothing in their background to suggest that at all.”

Residents of the area felt a grim sense of deja vu. Four months after their quiet corner of England was plunged into a Cold War-style saga of spies, chemical weapons and international tensions, they wondered whether it was happening all over again. Britain accuses Russia of attacking the Skripals; Russia denies it.

“With the Russian attack happening not long ago, we just assumed the worst,” said student Chloe Edwards, who said police and fire engines descended on a quiet street of newly built homes in Amesbury on Saturday evening.

Edwards said she saw people in green suits — like those worn by forensics officers — and her family was told to stay indoors for several hours.

Police said officers were initially called Saturday morning about a collapsed woman, then were summoned back in the evening after a man fell ill at the same property. Police at first thought the two, identified by friends as 44-year-old Dawn Sturgess and 45-year-old Charlie Rowley, had taken a contaminated batch of heroin or crack.

Initially, the investigation was led by local police, but Basu said counterterrorism detectives were taking charge after the substance was identified as Novichok. He said 100 officers had been assigned to the case.

Prime Minister Theresa May’s office said she was being kept updated on the case, “which understandably is being treated with the utmost seriousness.” The government’s emergency committee, known as COBRA, met today and was due to convene again Thursday.

Even before the poison was confirmed as Novichok, the emergency services’ response echoed that in the case of Sergei Skripal, 67. The former Russian intelligence officer was convicted of spying for Britain before coming to the U.K. as part of a 2010 prisoner swap.

He had been living in Salisbury, a cathedral city 90 miles (145 kilometers) southwest of London, when he was struck down along with his 33-year-old daughter Yulia, who was visiting him.

The Skripals’ illness initially baffled doctors after they were found unconscious on a park bench in Salisbury. Scientists at the Porton Down defense laboratory concluded they had been poisoned with Novichok, a type of nerve agent developed by the Soviet Union during the Cold War.

After spending weeks in critical condition, the Skripals were released from the hospital and taken to an undisclosed location for their protection. Doctors say they don’t know the long-term prognosis.

Britain accuses Russia of poisoning the Skripals, a claim Moscow strongly denies. The case sparked a diplomatic crisis between Russia and the West, including the expulsion of hundreds of diplomats from both sides.

The two Amesbury victims were at Salisbury District Hospital, which also treated the Skripals. Police said the victims are British citizens and live in the area.

Neighbors on Muggleton Road in Amesbury, where Rowley is believed to live, said they did not know the couple well and didn’t know what they did for a living. Most residents have only recently moved to the new houses and apartments.

Sam Hobson, a friend of the couple, said he was with them on Saturday, when Sturgess fell ill first. He told Sky News she was “having a fit, foam coming out of her mouth.” Rowley collapsed later the same day.

“He was sweating loads, dribbling. … He was rocking backwards and forwards,” Hobson said. “There was no response from him. He didn’t even know I was there.”

Police cordoned off a home in Amesbury, believed to be Rowley’s, and other places the pair visited, including a church, a pharmacy and a park in Salisbury, near where the Skripals were found.

Salisbury and surrounding towns have only recently begun to recover from the frightening weeks at the center of an international spy drama.

Police from 40 departments in England and Wales returned home in June after months working on the Skripal case, and specially trained workers have spent months decontaminating sites around the city.

The British government has pledged 2.5 million pounds ($3.3 million) to local businesses to make up for lost revenue in the area, which is a gateway to Stonehenge, the ancient stone circle that is a huge tourist destination.

“Amesbury’s a lovely place — it’s very quiet, uneventful,” said resident Rosemary Northing. “So for this to happen, and the media response and the uncertainty, it’s unsettling.”

Justin Doughty, who lives across the street from the cordoned-off house, said residents want more information from the authorities.

“We don’t know, to be honest now, because is it linked to Salisbury or is it drug-related?” he said. “None of us is being told anything by the police, and it would be nice to know something.”