It started around 4:00 Monday afternoon on Country Club Place in Merced County.
50 firefighters from different agencies responded to the fire. They spent nearly 12-hours getting it contained.
One firefighter was taken to the hospital for a heat-related injury. Tuesday morning, investigators revisited the home.
Cal Fire officials tell Action News damage, which includes everything inside, is estimated at $3 million.
The owners were not home when the fire started.