Padiham holidaymakers returned home to find parts of their house gutted by fire.
The blaze is believed to have broken out at the Dryden Street address when the occupants were on holiday.
But they came home to find the kitchen destroyed and the rest of the house badly damaged by smoke.
Firefighters were called in to investigate the incident on Sunday at 13-48pm.
Acting crew manager Kevin Birchall, of Padiham Fire Station, said: “There was severe damage by fire to kitchen and substantial damage by smoke to majority of the house. There was a working smoke alarm at the property and, had it been occupied at the time of the fire, would have saved lives.”
He added: “When leaving you property to go on holiday, ensure that all your electrical appliances that do not need to be left on are switched off.”