Up to 100 fire fighters from across West Yorkshire spent more than four hours battling a fire in Dalton Mills, Keighley, last night.
The blaze gutted one four-storey wing of the 19th century Dalton Lane property.
Fire service personnel remained at the scene this morning, investigating the cause of the fire.
Crew commander Steve Bairstow, of Keighley Fire Station, said fire fighters were alerted to the incident shortly before 7pm last night.
He said the fire was confined to the wing of the property running along School Lane, facing the Burgess Ford car dealership.
He said he understood this part of the building had been unoccupied at the time.
He said the fire was not extinguished until about midnight, though fire crews remained on the scene well into the following morning, damping down the wreckage.
Crew commander Paul Turner said at the height of the blaze there were 20 fire engines present from across the county.
He added: "We’d got called out after reports of a building fire and because of the number of calls we had 10 pumps here within minutes.
"There were flames coming out of the roof and out of every window.
"We wanted to stop it from spreading to the rest of the building.
"Once we got into the Burgess Ford forecourt it was pretty straightforward to deal with the fire.
"But the building was still well alight by the time I left at 9pm."
Photos posted on an urban explorer website this morning show fire fighters using hoses mounted on aerial platforms to douse the flames.
Dalton Mills is owned by Wakefield-based property development firm Magna Holdings, and recently failed to sell at auction.
Last month (Dec 2010) the Keighley News reported that this company was in negotiations with two potential buyers for the historic complex.
Dalton Mills once employed more than 1,000 workers and in recent years has been used as the setting for television dramas and Bollywood films.