Firefighters were called to a blaze at an outbuilding next to an old pub.
A crew from Bamber Bridge was called to the Bay Horse in Preston Road, Whittle-le-Woods, near Preston, at around 3.20pm on Monday.
Two officers wearing breathing apparatus used two hose reels and a triple extension ladder to tackle the fire, after breaking into the property, near the junction with Kem Mill Lane and School Brow.
Phil Henry, crew manager, said the incident caused severe damage to timber stored in a first floor room and severe smoke damage to the rest of the room and its contents.
He said it appeared a pile of rubbish had been set alight, possibly by a group of youths, but said he could not confirm whether the fire had been started with the deliberate intention of damaging the building.
He said: “It was behind the old Bay Horse pub, in an old stone outbuilding there, like old stables.
“There was a fire in the first floor room. It may have been kids but I wouldn’t like to say it was started deliberately.
“We were there for around two hours.
“There were bits of old timber that had been stacked up, which were destroyed in the fire.”
The Bay Horse has been closed since last year.