The fire was reported around 10:30 p.m. Wednesday at a single-story home on the 13500 block of West Gager Street, according to the Los Angeles Fire Department.
Firefighters encountered raging flames engulfing a detached garage behind the property that was converted into a living space.
They were able to rescue a 39-year-old woman with special needs. She suffered severe burn injuries and was taken to a hospital in critical condition.
During the fire fight, crews discovered another person inside the converted garage. The woman, believed to be around 60 years old, was pronounced dead at the scene.
The relationship between the two women is unclear.
The cause of the fire has not been determined, but officials said the structure did not have smoke alarms or fire sprinklers.