Nineteen buses were destroyed in a fire in West Sussex during the early hours.
Emergency services have been on the site of the former Shoreham Cement Works, on Shoreham Road, Upper Beeding, since about 02:00 BST.
West Sussex Fire and Rescue said a neighbouring workshop had also been damaged by fire.
"Two historically important Southdown vehicles" were reportedly saved. It is not known what caused the fire.
West Sussex Fire and Rescue said an investigation had begun into the cause, but said it may have been started deliberately.
Adrian Carter, station commander, West Sussex Fire and Rescue, said crews arrived to find a series of coaches alight.
He told BBC South East Today they were "ordinary coaches that transport people around for holidays or to school".
The scene after the fire was "pretty devastating for the owners", he said.