EL CAJON, Calif -- A two-alarm fire of unknown origin Friday gutted an East County house and left the elderly homeowner with minor burn injuries.

The blaze in the 800 block of Grossmont Avenue in El Cajon erupted about 12:15 p.m. and quickly turned the single-story residence into an inferno.

"I saw it from City Hall (several miles away)," fire department spokeswoman Monica Zech said. "It was quite a huge plume of black smoke rising."

The owner of the home and her 53-year-old daughter were able to escape the flames safely, but the older woman sustained burns to her arms and scalp when she re-entered the burning house to rescue her pet Chihuahua.

She grabbed the animal and got outside again with help from a city public works employee, Zech said.

It took crews from several area firefighting agencies about 25 minutes to extinguish the flames.

Medics took the homeowner to nearby Grossmont Hospital in La Mesa for treatment of her burns. The younger woman and the dog were unharmed, Zech said.

A preliminary damage estimate set the monetary losses at $250,000.

The displaced women planned to stay with relatives in the area, so the American Red Cross was not called in to help them arrange for interim lodging, the spokeswoman said.

The cause of the fire, which erupted in the family room of the home, was under investigation.