British police declared a "major incident" Wednesday after two people were left in critical condition from exposure to an unknown substance a few miles from where a former Russian spy and his daughter were poisoned with a nerve agent.
The Wiltshire Police force said a man and a woman in their 40s were hospitalized after being found unconscious at a residential building in Amesbury, eight miles (13 kilometers) from Salisbury, where Sergei and Yulia Skripal were poisoned on March 4.
Police cordoned off the building and other places the two people visited before falling ill, but health officials said there was not believed to be a wider risk to the public.
The man and woman were hospitalized Saturday at Salisbury District Hospital, where Sergei and Yulia Skripal spent weeks in critical condition after being poisoned in March.
Police said they initially believed the latest victims might have taken a contaminated batch of heroin or crack cocaine.
"However, further testing is now ongoing to establish the substance which led to these patients becoming ill and we are keeping an open mind as to the circumstances surrounding this incident," police said. "At this stage, it is not yet clear if a crime has been committed."
A major incident is a designation allowing British authorities to mobilize more than one emergency agency.
Residents in the area, a quiet neighborhood of newly built houses and apartments, said they had received little information from authorities.
"Amesbury's a lovely place -- it's very quiet, uneventful," said Rosemary Northing, who lives a couple of hundred yards (meters) away from the cordoned-off building. "So for this to happen, and the media response and the uncertainty, it's unsettling."
Neighbors said police cars and fire engines descended on the home late Saturday. Student Chloe Edwards said she saw people in "green suits" -- like those worn by forensics officers -- and her family was told to stay in their home for several hours.
"We wanted to know what happened and with the Russian attack happening not long ago, and we just assumed the worst," said Edwards.
Britain accuses Russia of poisoning the Skripals with a nerve agent known as Novichok, a group of chemical weapons developed by the Soviet Union during the Cold War. Moscow denies the allegation. The poisoning sparked a Cold War-style diplomatic crisis between Russia and the West, including the expulsion of hundreds of diplomats from both sides.
Counter-terrorism teams from London's Metropolitan Police were called in to help local forces in Wiltshire at the time of the Skripal poisoning. On Wednesday, however, Scotland Yard referred media calls to Wiltshire police.
The statement from Wiltshire Police came only a month after police from 40 departments in England and Wales returned home after months of working on the Skripals' poisoning. Wiltshire Police spent about 7.5 million pounds ($10 million) dealing with the aftermath of the Skripals' poisoning and believe that his front door was contaminated with the nerve agent.
Sergei Skripal, 66, is a former Russian intelligence officer who was convicted of spying for Britain before coming to the U.K. as part of a 2010 prisoner swap. He had been living quietly 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.
After being found unconscious in the street, the two spent weeks in critical condition at the hospital. Doctors who treated them say they have made a remarkable recovery but they still don't know what the Skirpals' long-term prognosis is.
The Skripals have been taken to an undisclosed location for their protection.