A fire that claimed the life of an elderly Petaluma woman in her mobile home Thursday may have been caused by an electrical cord or portable heater.

Petaluma Fire Marshal Cary Fergus said Friday the origin is undetermined, but likely involved a heating device being used in the living room of Elizabeth "Betty" Ferry.

Ferry, a feisty Texan who turned 88 on New Year's Eve, had lived at the Leisure Lake Mobile Home Park for about a decade, neighbors said.

Neighbors called 911 around 3 p.m. Thursday to report Ferry's single-wide coach on fire at the north Petaluma mobile home park.

A next-door neighbor said he tried to open Ferry's door but it was too hot.