Fire crews spent almost four hours tackling a blaze at a disused restaurant in Lostock Hall.
Fire-fighters from Bamber Bridge, Leyland and Penwortham fire stations were called to what was The Wesley House in Watkin Lane at around 9.30pm on Tuesday night.
They remained at the scene of the fire, which is being treated as suspicious, until 1am yesterday morning.
Watch manager from Bamber Bridge fire station Tony Spencer said: “Somebody had seen flames at the rear of the property, when we got there the rear extension of the property was quite well alight.”
Crews managed to contain the fire to the rear extension which was severally fire damaged and there was smoke damage to the rest of the property.
A fire investigation has now been launched.