Sauk County Sheriff's Department was planning to search the area throughout the night to see if there were any passengers from the helicopter, said Randy Stammen with the department.
Investigators found one body but hadn't been able to reach it at that time, Stammen said at a press conference.
The occupants escaped the house about two miles north of Prairie du Sac before flames engulfed it. One person in the home was uninjured and the other two received minor cuts and bruises. One of the two was taken to a hospital, and the other refused treatment.
The helicopter also damaged power lines in the area, said Annemarie Newman, spokeswoman for American Transmission Company.
The accident occurred at about 8 p.m.
It is unclear where the helicopter was from or what it was doing in the area, Stammen said. It traveled east over Lake Wisconsin before crashing.
According to witnesses, the helicopter became tangled in some power lines.
Haakon Carlson and three others were returning from a boat ride on Grubers Grove Bay when they saw the helicopter. Carlson said he first thought the pilot was trying to ``buzz'' the bay area because of it was flying very low.
Then the four saw high power lines swinging and the helicopter clipping the lines and losing control, Carlson said. He also saw debris falling from the helicopter before it crashed.
``We saw it tumbling over us,'' he said. ``Fortunately for us the momentum carried its parts over our heads and beyond us. Almost after it was overhead we realized it was coming apart and losing control.''
The fire at the house was still burning but under control Friday night, said Jim Kirch, Sauk City Fire Captain.
