The blaze was reported at about 9:45 a.m. at a two-story home at 3243 San Luces Way and was brought under control a few hours later.
Smith said ammunition and firearms were stashed in the room where the fire originated. The ammunition exploded as the flames spread, forcing firefighters to battle the blaze from the outside.
"We don't get a fire with live ammunition too often," Smith said.
No one was injured, but he said the home has been deemed uninhabitable. The American Red Cross has been called to assist seven residents.