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The couple fighting for their lives after being poisoned with a nerve agent may have been contaminated after “dumpster diving” for items in skips and outside charity shops, according to a friend.

Counter terrorism police are scouring the homes of Dawn Sturgess, 44, and Charlie Rowley, 45, amid fears they stumbled on a container holding the military-grade Novichok poison after it was discarded by a Russian hit squad.

The couple were taken ill on Saturday in Amesbury, around eight miles from where former Russian spy Sergei Skripal and his daughter were poisoned with the same substance in Salisbury in March.

Today a long-time friend of the pair said the pair would often trawl through bins in search of items discarded by charity shops.

Justin Ling, 47, who was among fellow residents evacuated from the hostel where mother-of-three Ms Sturgess lives and who has known Mr Rowley for fifteen years, said: “They used to go dumpster diving outside of charity shops, going through the stuff they used to chuck out.

“They would find stuff and get bits of jewellery to get some money. They could have been contaminated there.”

He added: “My friend has been to see them and they are both unconscious, the doctors said they weren’t responding to treatment.

“She was just getting back on her feet before this happened. They are a good couple, very much in love and they are good for each other. They’ve had their troubles but were both in treatment.”

Police suspect that the pair may have found a vial or syringe used to transport the Novichok used in the attack on Mr Skripal, and his daughter Yulia in March. They spent weeks in hospital before being discharged.

There has also been speculation that the nerve agent may have been on a tainted cigarette butt.

The development has raised questions over why the police and authorities failed to alert locals to the possibility that deadly materials could have been left lying around the city.

England’s chief medical officer yesterday urged people not to pick up “any unknown or already dangerous objects.”

Whitehall officials have denied that there was a failure to properly clean-up in Salisbury after the Skripal attack, saying none of the areas involved featured in the original decontamination process.

Some experts say that the poison would degrade if it had been left outside and exposed to the elements so it is more likely it was protected in an enclosed space.

However, one of the inventors of Novichok told The Independent that the nerve agent was ““near impossible” to detect and could remain potent for years to come.

Vladimir Uglev, who worked on the substances for 15 years, said : The substance can absorb itself into any soft surface, whether trees, leather, or park benches. From there it can be absorbed onto people’s skin with all the consequences.”

Six sites visited by Mr Rowley and Ms Sturgess in Salisbury and Amesbury before they fell ill have been cordoned off, including the Queen Elizabeth Park in Salisbury and a Boots chemist and a baptist church in Amesbury.

But the focus appears to be on the couple’s two homes and metal barriers and four forensic tents have been erected outside Ms Sturgess’s hostel John Baker House in the city centre.

Mr Rowley’s home on Muggleton Road, Amesbury has also been sealed off.

Land Rovers and large transit vans have been carrying supplies to the search while business owners have been kept in the dark over how long the searches will take.

Russian Spy Sergei Skripal: Salisbury Nerve Agent Incident 14 show all Russian Spy Sergei Skripal: Salisbury Nerve Agent Incident 1/14 Investigators in protective gear pursue the probe into the nerve agent attack on Sergei Skripal Getty 2/14 Russian spy 'poisoning': Sergei Skripal and Yulia Skripal are fighting for life in hospital PA 3/14 Personnel in hazmat suits work to secure a tent covering a bench in the Maltings shopping centre in Salisbury, where former Russian double agent Sergei Skripal and his daughter Yulia were found critically ill by exposure to a nerve agent Andrew Matthews/PA 4/14 ilitary personnel are deployed to help remove vehicles from the scene after former Russian double agent Sergei Skripal and his daughter were found critically ill after exposure to a nerve agent in Salisbury Getty Images 5/14 Military in protective clothing remove vehicles from a car park in Salisbury EPA 6/14 Police cordon: Military personnel in Salisbury PA 7/14 Traces of the nerve agent used to poison Sergei Skripal and his daughter Yulia were found at Zizzi in Salisbury PA 8/14 Amber Rudd: she visited the scene where Sergei Skripal and his daughter Yulia were found after having been poisoned by a nerve agent REUTERS 9/14 Personnel are helped from their hazmat suits (right), after securing a tent covering a bench in the Maltings shopping centre in Salisbury, where former Russian double agent Sergei Skripal and his daughter Yulia were found critically ill by exposure to a nerve agent Andrew Matthews/PA 10/14 Personnel in hazmat suits walk away after securing a tent covering a bench in the Maltings shopping centre in Salisbury, where former Russian double agent Sergei Skripal and his daughter Yulia were found critically ill by exposure to a nerve agent Andrew Matthews/PA 11/14 Police put a red bag inside a police evidence bag immediately after the nerve agent attack on a Russian spy. Officers previously issued CCTV of a woman clutching a red bag Solent news 12/14 Snap Fitness 24/7 13/14 Police activity in the cul-de-sac in Salisbury that contains the home of former Russian double agent Sergei Skripal who was poisoned along with daughter Yulia with a nerve agent PA 14/14 Sergei Skripal shops at Bargain Stop in a CCTV image from five days before his apparent poisoning 1/14 Investigators in protective gear pursue the probe into the nerve agent attack on Sergei Skripal Getty 2/14 Russian spy 'poisoning': Sergei Skripal and Yulia Skripal are fighting for life in hospital PA 3/14 Personnel in hazmat suits work to secure a tent covering a bench in the Maltings shopping centre in Salisbury, where former Russian double agent Sergei Skripal and his daughter Yulia were found critically ill by exposure to a nerve agent Andrew Matthews/PA 4/14 ilitary personnel are deployed to help remove vehicles from the scene after former Russian double agent Sergei Skripal and his daughter were found critically ill after exposure to a nerve agent in Salisbury Getty Images 5/14 Military in protective clothing remove vehicles from a car park in Salisbury EPA 6/14 Police cordon: Military personnel in Salisbury PA 7/14 Traces of the nerve agent used to poison Sergei Skripal and his daughter Yulia were found at Zizzi in Salisbury PA 8/14 Amber Rudd: she visited the scene where Sergei Skripal and his daughter Yulia were found after having been poisoned by a nerve agent REUTERS 9/14 Personnel are helped from their hazmat suits (right), after securing a tent covering a bench in the Maltings shopping centre in Salisbury, where former Russian double agent Sergei Skripal and his daughter Yulia were found critically ill by exposure to a nerve agent Andrew Matthews/PA 10/14 Personnel in hazmat suits walk away after securing a tent covering a bench in the Maltings shopping centre in Salisbury, where former Russian double agent Sergei Skripal and his daughter Yulia were found critically ill by exposure to a nerve agent Andrew Matthews/PA 11/14 Police put a red bag inside a police evidence bag immediately after the nerve agent attack on a Russian spy. Officers previously issued CCTV of a woman clutching a red bag Solent news 12/14 Snap Fitness 24/7 13/14 Police activity in the cul-de-sac in Salisbury that contains the home of former Russian double agent Sergei Skripal who was poisoned along with daughter Yulia with a nerve agent PA 14/14 Sergei Skripal shops at Bargain Stop in a CCTV image from five days before his apparent poisoning

Wiltshire Police initially thought the pair had fallen ill after using a contaminated batch of heroin or crack cocaine.

But after tests at the government’s military research facility at Porton Down, a major incident was declared and it was confirmed the couple had been exposed to Novichok.

The second nerve agent emergency in four months has prompted a diplomatic row, with Home Secretary Sajid Javid accusing the Russian state of using Britain as a “dumping ground for poison”.

The Russian Embassy hit back, accusing the Government of trying to “muddy the waters” and “frighten its own citizens”.