A 64-year-old woman found dead Monday after a fire tore through her Ocean Avenue apartment is believed to have died before the flames erupted in her living room, police said Wednesday.

The death is not considered suspicious.

Linda Butterworth, 64, was found dead inside her unit at 609 Ocean Ave. after neighbors reported the fire after 4 p.m. The state fire marshal’s office determined the fire was likely started by smoking materials that ignited fabric on a living room chair.

Police did not explain why they concluded Butterworth died before the fire broke out, although the case is being reviewed by the office of the Chief Medical Examiner. The office is awaiting final toxicology results before making a formal determination on the cause and manner of death.

Portland’s fire department credited working smoke detectors and fast-acting neighbors who called 911 for helping to limit the fire damage to one unit. About 25 to 30 tenants were temporarily displaced by the fire, although virtually all of the residents were allowed to return Monday night.