NEW CASTLE, Pa.—An 11-year-old girl initially unaccounted for during a fire at her mother's home was found safe at her father's residence in western Pennsylvania, though her 16-year-old brother remained in critical condition after narrowly escaping.

Investigators in Neshannock Township have released only the name of their mother, Jennifer Bees, who was awakened by a neighbor about 4:30 a.m. Wednesday before carrying another child, her 6-year-old daughter, to safety.

Bees returned to rescue her autistic teen son, but both had to be rescued by a township police officer. That's when Bees panicked, forgetting that her daughter was spending the night with her father, setting off a frantic 45-minute search for the girl.

Police were trying to determine whether an electric heater started the fire, about 45 miles northwest of Pittsburgh.

Bees' son remained in a Pittsburgh hospital.