Two people fell ill on Sunday when eating in a restaurant in Salisbury, the English city where former Russian agent Sergei Skripal and his daughter Yulia were poisoned in March, police said.
One of two people taken ill at a Salisbury restaurant is Russian, Sky News reported, citing sources. Police were called to the Prezzo restaurant in the evening in response to a "medical incident" involving a man and a woman, Wiltshire Police said in a statement.
"As a precautionary measure, the restaurant and surrounding roads have been cordoned off while officers attend the scene and establish the circumstances surrounding what led them to become ill," it said.
Britain has said Russian officers used the nerve agent Novichok to attack the Skripals. The Kremlin has denied any involvement.
Police have said a nerve toxin had been left on the front door of the Skripals’ home. They were found slumped in Salisbury city centre after visting the Bishop’s Mill pub and Zizzi, another Italian restaurant.
The former Russian spy and his daughter survived the murder attempt, but an unconnected woman, Dawn Sturgess, died in July and her partner Charlie Rowley fell ill after Rowley found a perfume bottle containing the same nerve agent.
Earlier this month British prosecutors identified two Russians they said were operating under aliases - Alexander Petrov and Ruslan Boshirov - whom they accused of trying to murder the Skripals with a military-grade nerve agent.
Britain charged the two men in absentia with attempted murder, and said the suspects were military intelligence officers almost certainly acting on orders from high up in the Russian state.
Two Russians resembling the men said on television on Thursday that they were innocent tourists who had flown to London for fun and visited the city of Salisbury to see its cathedral.
They surfaced a day after President Vladimir Putin said Russia had located Petrov and Boshirov, but that there was nothing special or criminal about them.