British police have declared a “major incident” after two people were exposed to an unknown substance in a town near where a former Russian spy and his daughter were poisoned with nerve agent.

In a statement, the Wiltshire Police forces say a man and a woman — both in their 40s — are in critical condition after being found in Amesbury, eight miles (13 kilometers) from Salisbury, where Sergei and Yulia Skripal were poisoned on March 4.

Police on Wednesday were cordoning off places the people visited before falling ill, but public health officials say there is not believed to be a wider risk. They were hospitalized Saturday for suspected drug overdoses.

Britain accuses Russia of poisoning the Skripals with a Novichok nerve agent. 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.

The statement from Wiltshire Police came only a month after police from 40 departments in England and Wales returned to their home assignments after months of working on the Skripals’ poisoning. The Wiltshire Police force 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 located 90 miles (145 kilometers) southwest of London, when he was struck down along with his 33-year-old daughter.

After being found unconscious in the street, the two spent weeks in critical condition at the hospital. Doctors who treated the Skripals said at the time said they expected them to die. They say they still don’t know what their long-term prognosis is.

Viktoria Skripal is back in Russia, where she is running for a seat in a regional legislature on the ticket of a Kremlin-controlled party. In appearances on Russian state-controlled television, she has said she doesn’t trust Britain to handle the investigation into the nerve agent poisoning. - AP