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.
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.