The military has arrived in Salisbury to start the clean-up operation following the poisoning of former spy Sergei Skripal and his daughter Yulia.
Serving personnel have begun the decontamination of what have been identified as the nine nerve agent "hotspots".
These include The Maltings, the cemetery, Zizzi and the Ashley Wood compound.
The work is expected to take a number of months and is currently being overseen by the Department for the Environment and Rural Affairs (DEFRA).
Earlier this month, it was announced that the Army and the Royal Air Force would support the clean-up operation in Salisbury, following the nerve agent attack in March.
Around 190 specialist military personnel from the Army and RAF will be supporting the operation to ensure the sites safe for public use.
Last week DEFRA’s Chief Scientific Adviser Ian Boyd, who is chair of the decontamination science assurance group overseeing the work, said:
"Our approach is based on the best scientific evidence and advice to ensure decontamination is carried out in a thorough and careful way."
"Our number one priority is making these sites safe for the public, so they can be returned to use for the people of Salisbury."
However, the level of contamination at the sites is still unclear.
Public Health England have reaffirmed that the risk to the general public is low.
Residents and visitors will see more activity in the city as the work gets underway.