On July 6, 1997, about 1130 eastern daylight time, a Ryan, Navion, N91519, collided with an oak tree and the ground during an attempted forced landing in a cow pasture, 3 statute miles northeast of Cross City Airport, Cross City, Florida. The flight was being conducted under the provisions of Title 14 CFR Part 91, with no flight plan filed. Visual meteorological conditions prevailed. The pilot and three passengers sustained serious injuries and the airplane sustained substantial damage. The flight originated at Cross City Airport about 1115 hours. According to the FAA, a witness heard an engine sputtering from an airplane overhead. Seconds later, the witness heard the collision of the airplane with the tree. Upon arriving, at the accident site, the witness found the airplane wreckage in a cow pasture. Examination of the accident site disclosed that the airplane had collided with an oak tree. The examination also revealed that the right wing tip had collided with the ground. The examination of the airframe, flight controls, and engine assembly found no evidence of a mechanical failure or malfunction. One fuel tank was ruptured with no evidence of fuel or the odor of fuel at the site. The other tank was not ruptured and there was no evidence of fuel. In the pilot's report of the accident, he stated that was a loss of fuel pressure for unknown reasons. He also stated, the accident could have been prevented by verifying the fuel quantity before takeoff.