LADERA HEIGHTS -- Authorities are investigating the cause of a residential fire that left a woman dead in the unincorporated Ladera Heights area of Los Angeles County, officials said.

The fire at a two-story triplex at 5441 La Cienega Blvd. was reported just after midnight Monday.

Firefighters smelled smoke while responding to an unrelated medical assistance call in the area and found the source of the blaze, said fire Capt. Michael Brown of the Los Angeles County Fire Department.

The fire was put out in about 40 minutes.

Fire crews found the body of a woman in her 50s in an upstairs bedroom, where the fire began, Brown said.

She was pronounced dead at the scene.

There were no other reports of injuries.