On August 4, 1996, about 0935 eastern daylight time, a Piper PA-32-260, N3399W, registered to South West Florida Air, Inc., crashed while making a forced landing following loss of engine power at Live Oak, Florida, while on a Title 14 CFR Part 91 personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft received substantial damage and the private-rated pilot and three passengers were not injured. The flight originated from Clearwater, Florida, the same day about 0815. The pilot stated he departed Clearwater with full fuel. While en route, abeam the Ocala, Florida area, he changed fuel tanks from the right main tank to the left main tank. While turning on to final approach at 750-800 feet agl, for runway 25 at the Suwannee County Airport, the engine failed. He applied carburetor heat at this time and attempts to restart the engine were unsuccessful. While making a forced landing in a field, the aircraft collided with a fence and separated the wings. Post crash examination of the aircraft by an FAA inspector showed no evidence as to the cause of the engine failure. The carburetor contained uncontaminated 100LL aviation fuel and the fuel vent system was unobstructed. All fuel tanks were ruptured during the accident causing loss of all fuel. The engine was started and operated to 1800 rpm with no evidence of failure or malfunction. A higher rpm was not selected do to a bent propeller. The carburetor heat operated normally during the engine run. Carburetor icing probability curves showed the aircraft was operating in conditions conducive to visible carburetor icing at cruise power and serious carburetor icing at glide power.