FORMER spy Sergei Skripal and his daughter Yulia were poisoned with a nerve agent at Mr Skripal's home address, police believe.

Detectives think the pair touched the nerve agent on the front door of the house in Christie Miller Road, Salisbury.

They were found unconscious on a bench in the Maltings on Sunday, March 4 and remain in critical condition in hospital.

A Scotland Yard spokesman said: "As a result of detailed forensic and scientific examination, detectives believe the Skripals first came into contact with the nerve agent at their home address. Specialists have identified the highest concentration of the nerve agent, to-date, as being on the front door of the address.

"Detectives will continue to focus their enquiries around the home address for the coming weeks, and possibly months as the investigation continues. Officers will be carrying out thorough searches in the areas surrounding this address as part of the ongoing investigation and as a precautionary measure."

Deputy Assistant Commissioner Dean Haydon, Senior National Coordinator for Counter Terrorism Policing said: “At this point in our investigation, we believe the Skripals first came into contact with the nerve agent from their front door. We are therefore focusing much of our efforts in and around their address. Those living in the Skripals’ neighbourhood can expect to see officers carrying out searches as part of this but I want to reassure them that the risk remains low and our searches are precautionary.

“I’d also like to thank the local community for their continued support and understanding. The unique circumstances of this investigation means that officers are likely be in the area for several weeks and months.”

Around 250 counter terrorism detectives continue to work around the clock on the investigation, supported by a full range of experts and partners.

Officers continue to trawl through more than 5,000 hours of CCTV and examine over 1,350 exhibits that have been seized. Around 500 witnesses have been identified and hundreds of statements taken.

Traces of the nerve agent have been found at some of the other scenes detectives have been working at over the past few weeks, but at lower concentrations to that found at the home address.

Specialist search officers are now concluding their meticulous work at some of these scenes and as they do so, are handing these back to Wiltshire Police.

Wiltshire Police Deputy Chief Constable Paul Mills said: “The Wiltshire Police support to the Counter Terrorism Policing Network investigation remains ongoing and is likely to do so for a number of months. It is an extremely challenging investigation and police and partners continue to manage a number of unique and difficult issues. We thank the public for their continued support.

“I am however pleased to confirm that the following sites have been handed back to Wiltshire Police by the national investigation:

The Maltings

The Ashley Wood compound

London Road Cemetery

“The Counter Terrorism Policing Network continue to retain the remaining scenes for evidential purposes at this time.

“As we start to see scenes handed back by the national investigation, Wiltshire Police will now work with Wiltshire Council and other partners who are leading on the recovery process to assess and agree the next steps that need to be taken to safely return sites to the public. At all times public safety will remain the number one priority for all agencies involved.

“I would like to reiterate our thanks to the people of Salisbury for their patience and understanding. We are very aware of the impact the closure of these scenes has had on the local community and businesses and we are very grateful for the support and cooperation that has been, and continues to be, shown whilst the police investigation and recovery process takes place.”