British police have urged people in the Amesbury and Salisbury areas not to pick up objects containing liquids or gel following the poisoning of a couple with a nerve agent last month.

Chief Medical Officer Sally Davies said: "I want to emphasise to everyone in the Salisbury and Amesbury area that nobody, adult or child, should pick up any foreign object which could contain liquid or gel, in the interests of their own safety.

"This in practice means do not pick up containers, syringes, needles, cosmetics or similar objects, made of materials such as metal, plastic or glass.

"This is particularly important as families are starting to prepare for their children's summer holidays and so I am asking that people are extra vigilant.

To be clear: do not pick up anything that you haven't dropped yourself."

The advice from Public Health England remains that the overall threat to the public is low, but that everyone should avoid picking up strange objects.

Two people were exposed to the nerve agent Novichok in Amesbury on 30 June.

Dawn Sturgess, 44, died in hospital at the weekend and her partner Charlie Rowley remains critically ill in hospital.

Salisbury District Hospital has said there has been a "small but significant" improvement in his condition.

Mr Rowley is now conscious and is described as being critical but stable.

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In a statement, Ms Sturgess' family said her death has been devastating for them and "Dawn will always be remembered by us as a gentle soul who was generous to a fault."

A major counter-terrorism police investigation is taking place into how the couple were exposed to the chemical weapon.

The main line of inquiry is whether it is linked to the attempted murders of former Russian spy Sergei Skripal and his daughter Yulia in nearby Salisbury in March.

Assistant Commissioner Neil Basu, the UK’s most senior counter-terrorism police officer, said there would need to be a forensic link to definitively prove a connection.

Central to the investigation is John Baker House, the supported-living accommodation where Ms Sturgess lived; Mr Rowley's home in Amesbury, and Salisbury's Queen Elizabeth Gardens, which remains cordoned off.

Last night, police officers removed a car from an address in Swindon, which is 64km from Salisbury.

The vehicle is understood to belong to a member of the emergency services.

Wiltshire Police said members of the public should "not be alarmed" by the activity.