Fire crews were called to the New Fortune House Chinese restaurant in Garstang Road South, Wesham, at about 12.30am on Saturday.
Two fire engines raced to the scene after reports of a loud bang and an explosion, and arrived to find a gas cylinder had exploded, blowing a hole in the side of the building.
Nobody was in the restaurant, which was closed at the time, and crews said, thankfully, nobody was just outside the building as debris shot across the road.
Police were called to the scene to help with closing the roads while the debris was cleared.
Lancashire Fire and Rescue Service said the cause of the explosion was now under investigation by the Health and Safety Executive.
Crew Manager John Leach, from South Shore fire station, said: “There was quite a large hole in the wall and debris strewn across the road.
“There was quite a lot of damage, all the windows were blown out and it was quite badly damaged inside.
“We are not treating it as a deliberate act, but we are investigating it.
“Nobody was hurt as nobody was in the property - it was very lucky really.”