'Like popcorn': Hundreds of bullets explode during Arizona fire

Hundreds of rounds of ammunition exploded during a Sunday morning house fire in the US state of Arizona, striking one firefighter in the face with a bullet.

Gilbert Fire Department arrived at the scene to find a home’s garage and attic on fire.

Neighbors reported hearing explosions as firefighters fought the flames.

"All I heard was, 'Pop, pop, pop,' and (saw) billowing black smoke," a neighbor told KNXV-TV.

Another neighbor said the explosions were “like microwave popcorn going off”.

Hundreds of rounds of ammunition exploded, according to reports. A firefighter was hit in the face by a bullet, but his face mask prevented any serious injuries.

The cause of the fire is not yet known, but officials believe an explosion might have occurred when the homeowner was loading gun cartridges sparking the blaze.

He was taken to a hospital for treatment with burns to his face and hands.

Bullets from the fire have been found up to 300ft from the scene.