Charred stones and peeling paint were all that was left of the once dark-green house on Oahu Place after a fire ravaged the Costa Mesa property Tuesday morning.
Flames were already shooting out of the front windows of the house by the time fire crews arrived just after 6:30 a.m.
Firefighters broke down the front door to try to rescue the woman inside, but they encountered "pack rat" conditions that hindered their ability to move around the home, officials said.
"You could tell just by looking at the house that if she was in there, she was already gone," said neighbor Leona Laurie.
After about 30 minutes, firefighters found the woman, who authorities believe was in her 70s, in the front bedroom. The room was full of clothing and other items, said Deputy Fire Chief Fred Seguin.
She was pronounced dead at the scene.
The coroner has not released the identity of the woman nor the cause of death.
Neighbors described the woman as a recluse who lived in hoarding conditions for years.
Homes where hoarding has occurred are especially dangerous to residents, fire crews and the community during a blaze, said Darren Johnson, a fire inspector with the Orange County Fire Authority and an executive member of an Orange County task force created 10 years ago to address hoarding problems in homes.
"The combustibles inside the home just add to the volatile nature of the fire," he said. "It acts as kindling."
Officials believe the contents of the home at 1654 Oahu Place helped fuel the fire and made the rescue attempt more difficult.
Residents are also more likely to become trapped inside a "hoarding home," since hoarders often have things stacked floor to ceiling, Johnson said.
Charmaine Laurie, Leona's mother, has lived next door to the woman for decades in the Mesa Verde neighborhood. She said she wasn't surprised by what firefighters found when they entered the home.
The woman rarely took her garbage out, her pool had turned green and a volunteer group from a local church removed her lawn in March because it was dying, Charmaine Laurie said.
"As soon as they [firefighters] opened up the garage, you could see that it was full of garbage," she said.
The woman moved in with her mother about 20 years ago, and both had hoarding tendencies, neighbors said. When the mother died years ago, the woman's hoarding got out of control, they said.
Charmaine Laurie said the woman didn't have a job or a car and left the house only to walk to Starbucks or the library with Angus, her miniature Schnauzer.
Though the house was in disarray, the slender woman was always well-groomed, as was her dog, Charmaine Laurie said.
"That dog was her best friend," she said.
It is unclear whether the dog made it out of the house.