Fire investigator Rick Campos says the fire smoldered for up to 90 minutes before being seen on January 30.
Arriving firefighters found flames on both the front and back of the house.
Campos would not say how or where the fire was started.
No arrests and no other injuries have been reported.
Lancaster County records say the three-bedroom house was appraised at $127,300.
Campos says the house and its contents, worth about $50,000, were a total loss.