Firefighters rescued a San Bernardino woman from a three-alarm blaze that sparked an explosion, collapsed her roof and ravaged her home, largely because the building was so badly cluttered that crews had trouble reaching the flames, city fire officials said.

“We had to physically pull a ton of stuff out of the second floor so we could get to the fire,” said Capt. Mike Arvizo.

The smoke and flames were reported at 2:45 p.m. Thursday along the 3000 block of North Stoddard Avenue, about a block northeast of I-210 and E Street.

Initially reported as a brush fire, the incident turned hectic when firefighters learned a house was burning – and someone was still inside.

Dressed in brush-fire gear, firefighters hustled into the house and rescued the woman without face masks and air tanks.

The building was so cluttered that only one person at a time could move through the hallways and stairwells, Arvizo said.

A father and daughter had fled the building earlier, but medical problems made it difficult or impossible for the woman to escape without help, he said.

As for the fire, a preliminary investigation suggested an electrical malfunction outside the house sparked the flames, which spread to low-hanging tree branches and leaves, then entered the building through windows and the attic.

Then, a propane tank exploded in the backyard. Two cars burned. And firefighters were warned the house contained ammunition, Arvizo said.

The rescued woman was hospitalized, possibly suffering from smoke inhalation. A firefighter was treated for an eye injury.

At 3:12 p.m., fire officials ordered an emergency evacuation of all firefighters from the building. Soon afterward, part of the roof collapsed.

The blaze threatened nearby homes. And the flames were so intense that additional crews were summoned from Rialto, San Bernardino County Fire Department, Cal Fire and the San Manuel Indian reservation.

Firefighters knocked down the flames about 4 p.m.

The house is still standing, but the damage is extensive. The second floor and part of the first floor are gutted.

As the embers cooled, fire officials turned their attention to identifying who threw a rock that shattered a side window of a moving ladder truck while it was about half a block from the fire. No crew members were hurt.