Firefighters inspect remnants of Long Beach back house after explosion

Firefighters rushed to a Long Beach neighborhood on Monday after a possible explosion destroyed a back house. 
It happened around 11 a.m. at a property in the 2800 block of Gale Avenue, according to the Long Beach fire and police departments. The explosion completely destroyed the accessory dwelling unit, also known as a back house or granny flat. However, The adjacent main house sustained significant damage to its exterior walls. 
Firefighters remained at the scene to inspect the destroyed building. An ambulance took one man with burns to the hospital. The severity of the injuries remains unclear. 
Inspectors red-tagged the back house and yellow-tagged the main building. The American Red Cross is helping two adults and a child affected by the explosion.
The blast caused roughly 2,000 residents to lose power. However, crews fixed most outages within a couple of hours of the explosion. 
Investigators are trying to determine what caused the explosion.