A three-alarm fire that destroyed a hillside home just south of El Cajon was probably started by an electrical failure, but the exact cause may never be known.

That's because the charred remains of the two-story home in the upscale Mount Merritt neighborhood collapsed after the fire gutted the house, leaving investigators little to work with, fire officials said.

The fire was reported shortly before 3:10 p.m. Tuesday on Vista del Monte Drive overlooking Chase Avenue. The three people inside escaped, but one man suffered a burn on his right hand and a woman was treated for smoke inhalation.

Sixty firefighters from six departments battled the flames into the evening hours, but the house was destroyed long before then.

“There was so much wood in there, a lot of open beams,” said Leonard Villarreal, spokesman for the San Miguel Consolidated Fire Protection District. “It was a great-looking design, but very fire-friendly.”

Damage was estimated at $800,000. Fifteen engine companies from San Miguel, El Cajon, La Mesa, Lemon Grove, Santee and Cal Fire managed to keep the blaze from spreading to other homes, quickly extinguishing spot fires on the steep hillside.

Two firefighting helicopters, one from the San Diego Fire-Rescue Department and another from the county Sheriff's Department, took turns making passes overhead, acting as spotters for the firefighters on the ground. Neither made any water drops, however.

Several units remained at the scene overnight to guard against flare-ups, Villarreal said, but there was nothing they could to do stop the blackened frame of the house from eventually crumbling and collapsing, making the work of fire investigators all but impossible.

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