The nerve agent used to poison former spy Sergei Skripal and his daughter Yulia in Salisbury was delivered ‘in a liquid form’, the Government has said.
The Department for Environment, Food and Rural Affairs (Defra) said a ‘very small amount’ of the Novichok nerve agent was used in the attack.
The details emerged at a press briefing in Salisbury, where reporters were told the highest concentration was found at Mr Skripal’s house.
Clean-up work is set to begin at nine sites across the city, as a tenth, an area of the London Road cemetery – which was found not to be contaminated – will reopen to the public today.
Defra said: “We either know there is contamination there (in the nine sites) or we think there is a probability we could find contamination there.’
Salisbury residents have been warned to expect a step-up in activity as investigators wearing protective clothes remove items and chemically clean the areas.
MOST POPULAR TODAY ON YAHOO
Sergei and Yulia Skripal were discovered unconscious on a bench in Salisbury on 4 March.
Ms Skripal, 33, left hospital earlier this month, while her 66-year-old father is said to be slowly recovering.
The Government has blamed Russia for the poisoning, but Moscow denies having anything to do with the attack.