An ambulance parked outside the Westfield Shopping Center in El Cajon burst into flames and then exploded several times Thursday afternoon.
Tanks inside the ambulance caused it to explode at about 4 p.m., according to a representative for the Hearthland Fire Department, but officials do not know what started the blaze.
No one was reported injured in the explosion, which occurred outside the entrance to the Wal-Mart at 415 Parkway Plaza.
The EMTs who drove the ambulance said they attempted to access the extinguisher inside, but the fire was too close, so they could not reach it, according to witness Jesse Yuhas.
Heartland Fire Department extinguished the fire shortly after the explosion.