WATERVILLE – An apartment fire Thursday left one woman dead and a man and his young son seriously injured.

Officials say the fire broke out shortly after 6 a.m. in an upstairs apartment of a two-unit house on Riverview Street.

Fire Capt. David Lafountain said firefighters rescued 28-year-old Craig Sargent and his 2-year-old son, Matthew. They found 23-year-old Amber Mitchell in a back bedroom and she was pronounced dead at MaineGeneral Medical Center.

Public safety spokesman Stephen McCausland said Sargent and his son were taken to St. Mary’s Hospital in Lewiston, where they were being treated for smoke inhalation.

According to McCausland, investigators said the fire started in the living room and most likely was caused by careless disposal of smoking materials. He said a battery-operated smoke detector had been removed and was found in a kitchen drawer.