MIDDLETON, Pa.—State police in central Pennsylvania say a fire that critically injured a man and woman and also injured their four children has been ruled accidental.

Trooper Robert Hicks said the blaze reported at 1 a.m. Saturday originated in the living room of the home in Middletown in Dauphin County where a space heater was being used, but it's unclear whether the heater was the cause.

George and Heather Radabaugh were taken to Lehigh Valley Hospital-Cedar Crest, where they remained in critical condition in the burn unit Tuesday.

Seven-year-old Gabreana Radabaugh was taken to the hospital in critical condition but was later upgraded to stable, and a hospital spokeswoman said Tuesday she had been discharged.

Three other children, ranging in age from 12 to 18, were also treated but later released.