An item contaminated with novichok that left a Wiltshire man and woman fighting for their lives has not been recovered, the Guardian has learned, as the search to find it intensifies.

Investigators have started examining key sites visited by Dawn Sturgess and Charlie Rowley in the hours before they fell ill.

In searing summer heat, officers in protective hazmat clothing began searching a homeless hostel in Salisbury where Sturgess lived and Rowley’s property in Amesbury, where both fell ill last Saturday.

Investigators at the hostel appeared to be examining the front door. Residents at Rowley’s house in Amesbury said they had been told they would be swabbed to check their health.

Sources with knowledge of the investigation, being led by Scotland Yard’s counter-terrorism unit, confirmed that swabbing skin from Sturgess and Rowley proved crucial in determining they had been poisoned by novichok after handling it.

Scientists examined swabs taken from them as they lay critically ill in Salisbury district hospital. The greatest concentration of novichok was found on their hands. That led scientists at Porton Down to tell investigators that the couple had handled whatever the contaminated item was.

The poison is believed to have been transmitted via absorption through the skin, as it was in the case of Sergei and Yulia Skripal four months ago after novichok was smeared on the front door of their Salisbury home.

Sturgess and Rowley were not targeted for assassination, police believe, and their contamination is thought to be a result of the recklessness of whoever possessed the novichok.

Britain blames Russia for the assassination attempt that struck down Sergei Skripal and his daughter, using the nerve agent developed by the Russian military. Investigators believe the same batch poisoned the British couple but are awaiting scientific confirmation.

Theresa May is expected to discuss the use of novichok in the UK with Donald Trump when the two meet on Friday during the president’s UK visit. She will try to persuade him to raise the matter with Vladimir Putin at their Helsinki summit on 16 July, but her message to Trump will depend heavily on the outcome of the investigation of the latest incident in Amesbury.

Quick Guide What is novichok? Show Novichok refers to a group of nerve agents developed by the Soviet Union in the 1970s and 80s to elude international restrictions on chemical weapons. Like other nerve agents, they are organophosphate compounds, but the chemicals used to make them, and their final structures, are considered classified in the UK, the US and other countries. The most potent of the novichok substances are considered to be more lethal than VX, the most deadly of the familiar nerve agents, which include sarin, tabun and soman. Novichok agents work in a similar way, by massively over-stimulating muscles and glands. Treatment for novichok exposure would be the same as for other nerve agents, namely with atropine, diazepam and potentially drugs called oximes. The chemical structures of novichok agents were made public in 2008 by Vil Mirzayanov, a former Russian scientist living in the US, but the structures have never been publicly confirmed. It is thought they can be made in different forms, including as a dust aerosol. The novichoks are known as binary agents because they only become lethal after mixing two otherwise harmless components. According to Mirzayanov, they are 10 to 100 times more toxic than conventional nerve agents. Photograph: Matt Cardy/Getty Images Europe

Paramedic teams and firefighters were standing by in Salisbury and Amesbury as the search operation continued on Friday . The hostel was evacuated on Thursday and on Friday men in camouflage suits wearing breathing apparatus and gloves were seen removing items.

Firefighters and paramedics on standby in Amesbury on Friday. Photograph: Chris J Ratcliffe/AFP/Getty Images

Police have secured all the locations the couple were known to have visited in the hours before they collapsed but the Wiltshire police chief constable, Kier Pritchard, accepted they could not have “100% confidence” they had pinned down all the sites.

Prof John Simpson, an expert from Public Health England, said it was not possible to do a scan of the whole of Salisbury to find out if there was contamination in other sites. He said: “There’s probably very little of it [novichok] and you can’t test the environment easily for it.”

More details of the couple’s lifestyle have emerged. Friends said Rowley frequently scavenged in bins for odds and ends he could sell.

One friend, who asked not to be named, said: “I can only imagine he picked it up from the bins. He loved binning. Dawn did, too. Dawn and him had loads of stuff in their houses that they picked up. Loads of household things.” Another said: “Quite often he would come back with stuff. Bits of jewellery and old electrical items. He’d sell them for £20 to £30.”

Public health and council chiefs have warned people not to pick up unidentified objects.

Officials met at the government’s Cobra emergency committee on Friday afternoon to discuss the latest developments, chaired by the deputy national security adviser, Madeleine Alessandri.

Some Salisbury residents expressed concern and asked for more openness from the authorities.



Standing beside a cordon at Queen Elizabeth Gardens in Salisbury, a spot the pair are known to have visited, Tony Kesterton, a retired teacher, said: “I wish they would give us more information about it; perhaps they haven’t got any more.

“I will take precautions, but you have got to carry on with life. People are very resilient here. But it’s got to put off tourism.”

Jim Diment, 54, a market trader, said business had been difficult since the latest poisonings. “It’s back to square one. It’s not good,” he said.

The Guardian understands the novichok that harmed Sturgess and Rowley may have been in a sealed container left following the attack on the Skripals in March. Sources close to the investigation hinted that they may now know the identity of whoever targeted the Skripals.

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



On Thursday, the Metropolitan police said: “Following further tests of samples from the patients, we now know that they were exposed to the nerve agent after handling a contaminated item.

“Detectives are working as quickly and as diligently as possible to identify the source of the contamination. Meticulous and systematic searches are under way at a number of sites.”