LONDON -- Authorities have broadened their investigation into the nerve agent poisoning of an English couple, seizing a car in a third community in southwestern England. Police seized a car in the large town of Swindon as part of their probe into the death of 44-year-old Dawn Sturgess, who was exposed to Novichok, a military-grade nerve agent produced in the Soviet Union during the Cold War. Her partner Charlie Rowley, 45, is critically ill.

Police have said the working theory is that their exposure was linked to the earlier Novichok attack in March on ex-Russian spy Sergei Skripal and his daughter Yulia in the city of Salisbury.

This July 10, 2018 photo shows authorities transporting a vehicle connected to the ongoing nerve-agent incident in Amesbury. WITTER/@IAMSTREETY via REUTERS

Wiltshire Police tweeted Monday that the car was being "safely" removed and reminded the public that the risk of contamination with the agent was low.

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Salisbury Hospital says Tuesday that Rowley has experienced a "small but significant improvement" and is now conscious. The 45-year old is in critical but stable condition.

The hospital says in a statement that "while this is welcome news, clearly we are not out of the woods yet. Charlie is still very unwell."

In a statement, Sturgess' family said her death has been "devastating" for them.

"She would do anything for anybody, and those who knew Dawn would know that she would gladly give her last penny to somebody in need," the statement said, according to BBC News. "She had the biggest of hearts and she will be dreadfully missed by both her immediate and wider family."