Firefighters responded at about 5:20 a.m. to a blaze in a unit of a single-story duplex located at 201 Idaho Ave., Division Chief Mark Ramos said.
Firefighters arrived and found heavy smoke and fire coming from the windows and doors of the unit.
Crews controlled the fire in the living room, kitchen and attic, where the fire was concentrated. They cut holes in the roof to vent the fire and smoke out of the attic and stop it from spreading to the neighboring unit, Ramos said.
When they entered the unit where the fire had begun, they found a woman unconscious in her bed, Ramos said. Firefighters took her outside of the bedroom and tried to resuscitate her but were not successful. She was declared dead at the scene.
The victim has been identified as Catherine Blake, 58, according to the Santa Cruz County coroner's office.
Although the official cause of the fire is under investigation, a preliminary investigation indicates the fire was accidental and caused by an unattended cigarette, Ramos said.
"She either dropped a cigarette or disposed of it, but didn't know it wasn't out all the way," Ramos said.
It appears Blake, who lived alone, died from carbon monoxide poisoning, Ramos said. There was no fire damage in her bedroom, he said.
The fire originated in the living room, where firefighters found "an excessive amount" of fuel load, consisting of books, magazines, newspapers, and old records that contributed to the fire's spread, Ramos said.
The fire caused about $500,000 in damage to the structure and $75,000 to the contents of the unit, Ramos said.
The neighboring unit sustained moderate smoke damage but was not damaged in the fire, Ramos said. The Red Cross provided temporary housing for a displaced male tenant.