Arsonists set fire to a building in Station Road, Peterborough on Saturday afternoon.
Crews from Stanground and Dogsthorpe were called to the blaze in a container unit which had spread to involve a railway shed. A gas cylinder was also involved.
Crews used hose reels to extinguish the fire, dampen down the area and cut away.
Anyone with information should contact the police on 101 or the independent charity Crimestoppers anonymously on 0800 555111.