The fire was reported at early Monday morning, Los Angeles Fire Capt. Jaime Moore said. Firefighters found the mother, a son and daughter, huddled together in one room in the converted barn and the father was found a few feet from the front door.
None of the four had a pulse, though emergency crews were able to resuscitate the mother, Maria Estrada, 40. She was taken to the hospital in critical condition where she died, the Los Angeles Times reported Tuesday.
Uriel Estrada, 41, Isabel, 12, and Alejandro, 7, died at the scene.
Moore said there were no smoke detectors in the barn, which had been converted into a living space. Brian Weinberger, a lawyer for property owner Leonarda Aguilar, disputed the claim, saying smoke detectors "were provided" when the family moved in six weeks ago.
Luke Zamperini, a spokesman for the Los Angeles Department of Building and Safety, said the property's permits didn't allow for the building to be used as permanent residential housing.