Lafayette police responded to a report of a vehicle fire in the 900 block of Hunsaker Canyon Road at 6:18 p.m. on Dec. 4.
When they arrived, officers found the car, a 1990 Lexus LS 400, engulfed in flames and hanging partway over the edge of an embankment, Lee said.
Inside, investigators found human remains, which were later determined to be those of Eiko Sugihara, an 86-year-old North Richmond resident. Sugihara's cause of death could not be determined because her body was too badly burned in the fire, Lee said.
Detectives have found evidence that Sugihara was at Hilltop Mall in Richmond getting her hair done several hours before she died, but they still don't know how she ended up in Lafayette, Lee said.
She has family in the Bay Area, but doesn't seem to know anyone out on Hunsaker Canyon Road, which is an unpaved road that leads to rural unincorporated Contra Costa County.
Investigators are also still working to determine how her car caught fire, Lee said.
Anyone with information that could be helpful to the investigation is asked to call the sheriff's office at (925) 313-2632.