PORTLAND — A woman found dead at the Feb. 18 fire at 609 Ocean Ave. died before the blaze started, according to investigators.

Police Lt. Robert Martin said Linda Butterworth, 64, was found in the apartment where the fire started around 4 p.m.

Martin said investigators from the state fire marshal’s office determined the fire was started accidentally, likely by smoking materials that ignited a chair. The Office of the Chief Medical Examiner found Butterworth was not killed by the fire, Martin said.

“The cause and manner of death will not be determined until after toxicology testing is completed” he said. “However, they do not consider her death to be suspicious.”

The fire damage was limited to Butterworth’s apartment, Martin said, crediting working smoke detectors and a fast response from building tenants who called 911.