A total of 48 firefighters responded to the 700 block of Cleveland Street at 6:04 p.m. Wednesday.
When crews arrived, responding firefighters found the bedroom of the top floor unit apartment engulfed in flames. According to authorities, they knocked the fire down in about 13 minutes.
The elderly woman was taken to the County-USC Medical Center with severe burns but was shortly pronounced dead.
Her husband and adult son are in critical condition.
The cause of the fire was under investigation. It is not believed to be suspicious in nature.
Arson detectives have estimated the loss as $25,000 in damage to the structure and $6,500 in personal loss.