On September 10, 1999, at 1932 eastern daylight time, a Reichert MJ-77, N51MJ, operated by a commercially rated pilot, sustained substantial damage during a forced landing at Owosso Community Airport, Owosso, Michigan. The pilot sustained fatal injuries. The 14 CFR Part 91 personal flight was not operating on a flight plan. Visual meteorological conditions prevailed during the flight. The flight had departed Owosso Community Airport on runway 28 (3,800 feet X 75 feet dry/asphalt) and was returning to runway 10 at the time of the accident. A witness saw the pilot perform a preflight inspection of the airplane and watched the airplane's takeoff and return. The witness said that the airplane took off to the west. He stated that he saw contrails coming from the wings. He said that the trails were black in color. He said that the airplane turned back to the airport and was in level flight about 100 to 150 feet above the ground. He said the engine was running. He stated that the airplane nosed down and crashed on the north side of the runway. Another witness saw the airplane two to three miles from the airport. This witness said that the airplane was trailing smoke similar to the smoke oil trails used by airshow performers. He stated that the airplane had black fluid coming from the trailing edge of the wings. He stated that the airplane was in a bank when he saw it. The airplane impacted the grass on the north side of the runway 10. The airplane came to rest inverted approximately 10 feet north of runway 10 and 300 feet east of the approach end of runway 10. A Federal Aviation Administration investigator performed an on-scene examination of the airplane wreckage. The examination revealed that the entire rear fuselage was streaked with oil. The examination further revealed that the engine oil tank filler neck was found without its cap engaged. This filler neck and cap assembly has a positive locking feature when closed. The filler neck was found without any damage marks. The filler cap's locking tangs were found damaged. The pilot's logbook was reviewed. The logbook indicated the pilot flew a total of 11.1 hours in the accident airplane.