BATH - Maine fire marshal investigators believe the victim of a fatal apartment fire in Bath unwittingly caused the blaze by smoking while using oxygen.

Steve McCausland of the Maine Public Safety Department says the victim is believed to be 68-year-old Joseph Richards, who lived in the apartment.

McCausland says the fire broke out shortly after 5 p.m. Sunday.

Neighbors say they heard explosions before and during the fire, apparently from oxygen tanks that firefighters later found inside.