Lancashire Police said they were called to the scene of the explosion in Heysham at 2.40am on Sunday after reports that “a number” of houses on Mallowdale Avenue had collapsed.
Several residents of the area tweeted that up to three houses had collapsed, and emergency services sirens had been heard near the scene for a prolonged time.
“A major incident has been declared after we (were) called to terraced houses on Mallowdale Avenue. It has been reported that there has been an explosion at a property and firefighters are searching the collapsed property,” it said.
Lancashire Fire said on Twitter that 10 units were called to the terraced row and firefighters were searching a collapsed property.
Dan Knowles, who lives four streets away from the explosion, said he thought there had been an earthquake.