LONDON, July 4 (Xinhua) -- A British couple critically ill in hospital have been poisoned by the same nerve agent used in the recent attack on a former Russian agent and his daughter, London's Metropolitan Police confirmed late Wednesday evening.

Britain's most senior counter-terrorism cop, ACSO Neil Basu confirmed that a couple from Wiltshire have been exposed to the nerve agent Novichok, and are both critically ill in hospital.

Police are still investigating how the couple became to be victims of the nerve agent, but there is no suggestion they are linked to the security services.

The development will come as a major blow after a multi-million dollar decontamination operation was carried out following the attack in March which left former Russian spy Sergei Skripal and his daughter Yulia both fighting for their lives. They are now recovering at secret addresses in Britain.

Dawn Sturgess, aged 44, from Salisbury, and Charlie Rowley, 45, from nearby Amesbury, both fell ill and at first it was thought a batch of contaminated drugs may have caused them to become seriously ill.

Scientists at Britain's top secret lab at Porton Down confirmed to police Wednesday night that tests they had carried out showed Novichok was responsible.

In a statement at the Metropolitan Police HQ in London Basu said: "I can confirm tonight that there has been a significant development and that the Counter Terrorism Policing Network is now leading the investigation into this incident. This evening we have received test results from Porton Down that show the two people have been exposed to the nerve agent Novichok."

The drama started last Saturday morning when an ambulance was called to a residential address in Amesbury where a 44-year-old woman had collapsed. Five hours later an ambulance was called back to the same address where the 45 year old man had also taken ill.

Paramedics wearing protective clothing took the man to hospital where the woman was already being treated.

Basu added: "From initial assessment it was thought that the two patients had fallen ill after using drugs from a potentially contaminated batch. Following the detailed analysis of samples 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."

He said the latest update from the hospital in Salisbury is that both patients remain in a critical condition. Both are British nationals and are local to the area.

Basu said at this stage no-one else has presented with the same symptoms linked to this incident.

"The priority for the investigation team now, is to establish how these two people have come into contact with this nerve agent," he added.

Around 100 detectives from the Counter Terrorism Policing Network are now working on the investigation, alongside officers from Wiltshire Police.

He said a number of sites in the Amesbury and Salisbury areas that police believe the two individuals visited in the period before they fell ill were cordoned off by police last night.

Basu added: "This is a precautionary measure while we continue to investigate how they came into contact with the substance. I do want to reassure the public that there is no evidence that either the man or woman recently visited any of the sites that were decontaminated following the attempted murders of Sergei and Yulia Skripal."

He said over the coming days people in the area can expect to see an increased police presence, which will include officers wearing protective equipment as they carry out activity at a number of sites.
Last month the heir to the British throne, Prince Charles and his wife the Duchess of Cornwall, visited Salisbury and mingled with shoppers at the local market to reassure people that the city was now safe to visit.
Police have not yet given any clues about how or why the couple were exposed to the nerve agent, but Basu said: "I would add that the complex investigation into the attempted murders of Yulia and Sergei remains ongoing and detectives continue to sift through and assess all the available evidence and are following every possible lead to identify those responsible, for what remains a reckless and barbaric criminal act.
"We are not in a position to say whether the nerve agent was from the same batch that the Skripals were exposed to. The possibility that these two investigations might be linked is clearly a line of enquiry for us," he said.