Firefighters were called after a blaze broke out in a car park under a former casino.
Fire crews went to the car park under the former Sam Tai casino bar and restaurant in Bloomfield Road, Blackpool, where a mattress and some carpet was on fire.
Smoke from the blaze had spread into the premises and set off the alarm, at about 1pm on Sunday.
Nobody was hurt, but police were called as it was described as a “fire of suspicious origin”.
Firefighters had to force entry to the building to make sure the fire hadn’t spread inside.
A power saw was used, as well as a hose reel and ladder.