On 24 June, 1997, at 1840 eastern daylight time, a Mooney M20C, N6756N, was substantially damaged during a forced landing to a hay field near Bellwood, Pennsylvania. The certificated private pilot and passenger received minor injuries. Visual meteorological conditions prevailed for the personal flight that originated at Williamsport, Pennsylvania, about 1730, destined for Fort Wayne, Indiana. An IFR flight plan was filed for the flight conducted under 14 CFR Part 91. In a telephone interview, the pilot reported that he was in cruise flight at 4,000 feet when he heard a "pop", experienced a loss of engine power, and encountered smoke in the cockpit. The pilot stated that the airplane descended at 200-300 feet per minute after the power loss. He said that he made no power adjustments because he feared inducing a total loss of power. The pilot was in contact with the Cleveland Air Traffic Control Center, and requested vectors for landing at the nearest airport. The center controller provided vectors for the Altoona-Blair County Airport (AOO). During the descent, the oil pressure went to "zero", and the engine stopped producing power. The pilot reported that his vision was obscured out the windscreen and that he felt he would be unable to complete a landing at AOO. He selected an open hay field through a side window and performed the forced landing. A fire in the engine compartment was extinguished after landing. Examination of the engine by a Federal Aviation Administration Inspector revealed the following: "A hole was noted in the engine crankcase below the number one cylinder. ...The number one cylinder was then removed. A visual inspection was made. A connecting rod failure was noted on the number one and number two cylinders."