SACRAMENTO, California (Reuters) - Homicide detectives searching for a California fire chief suspected of fatally stabbing his girlfriend turned their attention to the state's massive mountain ranges on Thursday, saying he may be hiding out along trails and backroads.

The Sacramento County Sheriff's Department said Orville "Moe" Fleming, a 55-year-old battalion chief with the California Department of Forestry and Fire Protection, has deep knowledge of the Sierra and Santa Cruz mountains and the picturesque Yosemite Valley.

Fleming, who has fire department keys giving him access to gated trails and roads, disappeared a week ago after his 26-year-old girlfriend, Sarah Douglas, was found stabbed to death at the home they shared.

The hunt for Fleming, believed to be armed, comes just over a year after former Los Angeles policeman Christopher Dorner fled into Southern California mountains after a murderous rampage targeting police officers and their families. That case ended in a fiery standoff that left Dorner dead.

The Fleming case has not yet sparked the same kind of intense manhunt undertaken for Dorner, in which hundreds of officers joined, in part because he had targeted law enforcement officials and their families.

Investigators said Thursday they have not yet been able to narrow down Fleming's location, and hope public attention could bring reports of sightings to help mount a targeted search.

The case took a prurient turn when sheriff's investigators said someone from an escort service may have helped Fleming evade capture.

"Investigators have discovered that Fleming has had contact with many escorts he met through the website "My Redbook," the sheriff's department said on its Facebook page.

After the murder, the fire department car that Fleming used was found abandoned in a Sacramento suburb, the department said.

"Investigators are looking into the possibility that someone Fleming knew, either through his contact with escorts, or through his personal or professional life, picked him up and drove him away," the Facebook post said.

Fleming has been fired from his job for not showing up for work from April 30, California Department of Forestry and Fire Protection spokesman Daniel Berlant said.

The sheriff's department, in a separate Facebook posting on Wednesday, noted that Fleming had changed his appearance in the past by shaving his head and mustache. He frequently wears a baseball cap and has tattoos on his left arm and bicep, it said.

Even though a week has passed since Douglas' death, her assailant would probably have sustained cuts on his hands and arms that would require bandages, investigators said. They said Fleming owned two pistols and should be considered armed and dangerous.

(Editing by Cynthia Johnston and Eric Walsh; Editing by Clarence Fernandez)