Firefighters believe a fire at a council storage depot in Buckinghamshire was started deliberately.
The fire broke out in the building at South Fifth Street, Milton Keynes, at just before 2300 BST on Friday.
A Buckinghamshire Fire Service spokesman said half of the roof of the building was damaged in the fire.
He said six firefighters in breathing apparatus tackled the fire, which took over an hour to bring under control.
The spokesman said arson was suspected.
Anyone with information is asked to call the police at Milton Keynes or Buckinghamshire Fire Service.