Blount County firefighters responded early this morning to a house fire on Mutton Hollow Road in Maryville.

Fire Chief Doug McClanahan said the call was reported about 5 a.m. A woman in the residence heard the smoke alarm and called 911. Firefighters found the fire in the basement. When they opened the door, gas or backdraft caused the fire to blow outward, causing an explosion in the main level of the house.

The force of the explosion blew out walls, broke windows and blew the home’s sun porch off its foundation.

Two firefighters were injured in the blaze. One was treated at the scene and was able to resume battling the blaze. The other had to be taken to Blount Memorial Hospital; he was treated and released.

The cause of the fire is under investigation.