Health chiefs said the risk to the public was low, repeating their earlier advice that the public should wash their clothes and use cleansing wipes on personal items.
Preliminary results indicated Tuesday that they may have been exposed to a nerve agent and police told reporters on Wednesday it was Novichok. "There is nothing in their background to suggest that at all", Basu said.
Russian Federation responded to the criticism from London by saying Britain was trying to frame Moscow for the latest poisoning.
Police say possibility that the two incidents are linked remains a key line of the inquiry.
If the Novichok was from a previous batch, Mirzayanov told ABC News, it would have had to have been stored in a secure vial or container, which may have been picked up by the Amesbury couple and caused them to fall ill. The couple, named locally as Dawn Sturgess 44, and Charlie Rowley, 45 were taken to Salisbury District Hospital on Saturday and are in a critical condition. Sam Hobson, a friend of the pair, confirmed their names in an interview with Agence France-Presse.
Investigators have yet to determine how Sturgess and Rowley came into contact with the nerve agent, but they've closed down sites in Amesbury and Salisbury where the victims are thought to have traveled before they were found sick.
Police say Sturgess and Rowley were poisoned by the same lethal toxin developed by the Soviet Union that nearly killed Skripal and his daughter in March. On Monday, due to concerns over their symptoms, samples from both patients were sent to a laboratory for analysis.
Russian Foreign Ministry Ministry spokeswoman Maria Zakharova is also urging London to allow Russia to investigate the March poisoning of former Russian spy Sergei Skripal and his daughter, along with British investigators.
"Two drug addicts were poisoned with serious drugs and the British intelligence services and the British leadership are now trying to interpret this incident as a continuation of the Skripal poisoning", said Peskov.
Scotland Yard's counter-terror team, who is leading the investigation, has not released the names of any suspects in connection with the Skripal poisoning.
"I understand that many people will be concerned".
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At around 12:20 pm on Friday 29th June the man and woman are together at John Baker House in Salisbury.
- Wipe personal items such as phones, handbags and other electronic items with cleansing or baby wipes and dispose of the wipes in an ordinary domestic waste disposal.
They failed to kill the target, and have so far managed to poison four defenceless people.
The agent is so potent that only a small amount would be needed to cause death, he said, adding it could remain deadly after several years if stored in a secure environment.
Authorities believe that Sergei and Yulia Skripal first came into contact with Novichok at Sergei's home.
The Skripals' illness initially baffled doctors after they were found unconscious March 4 on a park bench in Salisbury.
London had pinned responsibility for the attack on Moscow then.
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