Four more Russians are suspects in Novichok's investigation, but they have not yet been named, it was asserted tonight.
According to reports, security sources said that the Russian assault squadron that attacked the former spy Sergei Skripal had six members who were known as The Cleaners.
Alexander Petrov and Ruslan Boshirov were accused this week of carrying out the poisoning in Salisbury and were identified as members of the GRU, Russia's military intelligence service.
It is said that the assassination attempts had a backup team that traveled separately and helped with the reconnaissance in Salisbury, the Mirror reported.
Alexander Petrov and Ruslan Boshirov (pictured) were accused this week of carrying out the poisoning in Salisbury and were identified as members of Russia's military intelligence agency.
A source told the newspaper: "A backup is needed to keep the Skripals under surveillance. Petrov and Boshirov needed to know that they would not appear while they sprayed the novichok.
The backup team was also there in case something happened to the nerve agent, the source said.
It is also said that the two alleged murderers have visited the United Kingdom several times, posing as rich Russians, so their trip in March would not arouse suspicion.
It arrived when work began to decontaminate the home of the poisoning victim Mr. Skripal, six months after the attack.
A cordon has been established so that police investigations or cleanup work can be carried out safely and will remain in place until decontamination is complete.
The anti-terrorist officials believe that in the house Mr. Skripal, a former Russian agent, and his daughter Yulia were contaminated with neurotoxic agents on March 4, after a high concentration of the chemical weapon was found at the front door.
Military personnel wearing protective clothing begins to decontaminate the home of Sergei Skripal, the former spy who was targeted by the Novichok attack in Salisbury in March
The cleaning is being supervised by the Department of Environment, Food and Rural Affairs in association with the Wiltshire Council and carried out by specialized military teams.
Former GRU officer Mr. Skripal and his daughter Yulia became seriously ill after being exposed to the military-grade nerve agent Novichok in Salisbury in March.
Detectives believe it is likely that the two suspects, who are believed to be around 40 years old, travel under alias and that Petrov and Boshirov are not their real names.
Prosecutors consider it useless to ask Russia for the extradition of the two men, but a European arrest warrant has been obtained and the authorities are also seeking the help of Interpol.
Officials formally linked the attack to the Skripals with events in the vicinity of Amesbury when Dawn Sturgess, 44, and her partner Charlie Rowley, 45, were exposed to the same nerve agent. Mrs. Sturgess died later in the hospital.
Moscow has continued to deny that it was involved in the attack.
Former GRU officer Mr Skripal and his daughter Yulia (pictured together) became seriously ill after being exposed to military-grade nerve agent Novichok in Salisbury in March