On December 26, 2015, about 1340 mountain standard time, an Aerostar Aircraft Corporation of Texas M20F airplane, N6811V, was substantially damaged when it was involved in an accident near Nogales, Arizona. The pilot and three passengers were seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. Shortly after departure from Nogales International Airport (OLS), Nogales, Arizona, for a cross-country flight, the airplane impacted a hillside about .5 miles east of the airport and then came to rest upright on its belly. No mayday call was received from the pilot. During postaccident examination of the airplane, one of the landing gears was found separated, and the engine was found partially separated from the airframe, but it remained in its relative normal position. The airframe was substantially damaged. Fuel was observed leaking from the airplane, no holes were found in the engine case, and no evidence of leaking oil was found. The propeller assembly remained attached to the engine. One propeller blade was missing the tip, and the other propeller blade exhibited chordwise striations and was bent near the propeller hub. Examination of the airplane revealed no evidence of any preaccident mechanical malfunctions or failures that would have precluded normal operation; however, the engine was not examined. The pilot did not return the National Transportation Safety Board Pilot/Operator Report Form 6120.1 nor did he provide a statement about the accident sequence.