SAN DIEGO (AP) _ An 8-year-old girl was found dead and her parents and young brother unconscious, said authorities, who believed carbon monoxide from a heater was to blame.

David Keefe, 36, and Rosario Keefe, 39, were in fair condition today and their 5-year-old son, David, was in serious condition at University of California, San Diego Medical Center, hospital officials said.

Authorities found the family in their Imperial Beach apartment Wednesday afternoon after a call from neighbors brought them to the scene, said San Diego County sheriff's Sgt. Conrad Grayson.

Roseanne Keefe was pronounced dead at the scene, authorities said.

An autopsy was to be conducted today, said Jack Larkie, deputy county coroner.

Neighbors entered the apartment after they hadn't seen the family for two days, Larkie said.

About two days ago, the family had turned on a gas wall heater for the first time this winter, he said. He said a rag was found stuffed into the heater's vent, allowing carbon monoxide gas to accumulate in the apartment.