An industrial unit in Clevedon Road, North Shore, was left a blackened shell after a fire tore through it earlier this morning.
Station manager Colin Hickson, from Lancashire Fire and Rescue Service, said the building was already an inferno by the time crews arrived shortly after 4.15am.
It is thought the blaze went unnoticed for some time before being seen by a neighbour, who dialled 999 after spotting flames.
The roof has collapsed, as has an interior floor, but similar units on either side suffered only minor damage thanks for firefighters' efforts.
Four fire engines attended, as did an aerial ladder platform, though ultimately that was not needed.
"The crews worked really quickly and really hard to stop the fire spreading to adjoining properties, and to keep business going in the area," Mr Hickson said.
Nobody was injured, and investigators now plan to work to establish a cause, with none being immediately obvious.
Firefighters began scaling down their efforts at around 6am, but were expected to remain on the scene for several hours damping down the two-storey unit.
An engineer from Electricity North West was also called out after the unit's power supply was isolated.
An assortment of industrial and engineering products were found inside the lock-up by crews, who cut their way in through metal shutters, but it is not clear whether the unit was being used on a day-to-day basis by a business, or just as storage.
Earlier, residents nearby had been warned to keep their windows and doors closed because of the thick smoke. That warning is no longer in place.