LONDON: A clean-up operation in the British city where a former Russian spy was poisoned began Tuesday, with officials saying the nerve agent used was delivered in "liquid form" and small quantities.
The attack on ex-double agent Sergei Skripal and his daughter Yulia on March 4 in Salisbury has damaged relations between Moscow and the West.
The environment ministry, which is in charge of the clean-up, said an area of the cemetery in Salisbury where Skripal's wife and son are buried was re-opened on Tuesday.
But nine other sites, including a pub and a restaurant the Skripals visited shortly before collapsing, remain closed off. Counter-terror police are gradually handing the sites over to specialist cleaning teams.
The work is expected to take several months.Around 190 specialist military personnel are supporting the operation.
Suspected sites are tested, items which may have been contaminated are removed for chemical cleaning and then re-testing, the department said.
The environment ministry's chief scientific advisor Ian Boyd said: "Thanks to detailed information gathered during the police's investigation, and our scientific understanding of how the agent works and is spread, we have been able to categorise the likely level of contamination at each site.
"Meticulous work is required."
The Skripals were found slumped on a bench in Salisbury, having earlier visited a pub and a restaurant.
Sergei Skripal, 66, remains in the city's hospital, though he is improving rapidly and no longer in a critical condition, doctors said in their last update on April 6. Yulia Skripal, 33, has been discharged and is continuing her recovery in a safe house.
The Group of Seven industrial powers condemned the attack "in the strongest possible terms" on Tuesday.
They agreed it was "highly likely" that Russia was responsible and there was "no plausible alternative explanation".
Moscow vehemently denies any suggestion of involvement.