On February 5, 1995, at 1240 central standard time, a Cessna 172, N739FZ, registered to Wings Inc. of St. Paul, Minnesota, was substantially damaged following a loss of engine power and subsequent forced landing on a frozen lake near Park Rapids, Minnesota. The pilot had just completed a touch and go landing at Park Rapids when the power loss occurred. The pilot and one passenger reported no injuries. The 14 CFR Part 91 local pleasure flight originated from St. Paul at 1030. No flight plan was filed and visual meteorological conditions prevailed at the time. According to the pilot, the flight was uneventful until after he executed a touch and go landing at Park Rapids on runway 13 and the airplane was on its initial climb. The pilot stated that he was busy dialing in Brainerd VOR when he realized that the airplane was barely climbing. He immediately scanned the instruments, checked the fuel selector, and verified that the carburetor heat, the mixture control, and the throttle were in the full forward position to ensure maximum engine power. At this time, the pilot stated the airplane was maintaining level flight but the engine power was slowly decreasing. The pilot made a left turn in an attempt to return to Park Rapids, but soon realized that he would not be able to make it back to the airport. The pilot stated that he then decided to make a forced landing on a frozen, snow covered lake. As the airplane touched down, the landing gear dug into the snow, the airplane experienced a rapid deceleration, and nosed over. Postaccident examination revealed no mechanical anomalies. Fuel samples were taken on the day of the accident. Ice crystals were found in the fuel sample. A surface weather observation from Park Rapids Airport was taken eight minutes after the time of the accident. The observation reported a measured ceiling of 25,000 scattered, 20 miles visibility, temperature 2 degrees, and dewpoint negative 12. The temperature and dew point spread at the time of the accident were not conducive to carburetor ice. The local area had apparently been experiencing large temperature variations within the preceding couple of days before the accident. The local temperature on the day following the accident was 40 degrees.