The fire broke out in the 19500 block of Green Valley Road, said Sgt. Cindi West with the King County Sheriff's Office.
Investigators believe the fire was an accident and likely caused by an electrical problem.
West said there were were no signs of foul play. She said the person who lived in the home has "medical issues," but it will be up to the medical examiner to determine if the body found inside was the homeowner and how he or she died.