Firefighters were investigating reports of smoke in a neighborhood 90 minutes before a fire killed a mother and her 2-year-old child in a converted garage.
The fire erupted before noon Wednesday and took 30 firefighters 9 minutes to extinguish.
Three fire engines responded an hour and a half before the fire a block away, but found nothing, according to the Los Angeles Fire Department.
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An internal investigation was launched into the firefighters' actions before the blaze. Details about the initial call, which they described as a "vicinity call," were not available.
The fire broke out in a cluttered converted garage -- one room with a kitchen and a bathroom. It was not immediately known if there was a working smoke detector, fire officials said.
The clutter hampered firefighters' access, said Deputy Chief Joseph Castro, with the Los Angeles Fire Department.
Little was immediately known about the victims. A neighbor described the woman only as Nancy and said she was a quiet, happy, and loving mother. She lived there with her boyfriend and two young sons.
The deaths are the 10th and 11th this year, a rate far outpacing the 2013 total of 20 fire deaths.
An 89-year-old World War II veteran died in a house fire Feb. 21 in the Mt. Washington neighborhood of Los Angeles.
An 80-year-old woman died in a fire Feb. 8.
In January, a fire in a detached garage claimed the life of a 61-year-old man in Winnetka.