The airplane impacted the paved surfaces and a wooded median on an interstate highway. A postaccident fire resulted. The outboard section of the right wing and several sections of the empennage, including the horizontal stabilizer, elevator, and rudder, were found about 1/4 mile southwest of the fuselage, in a residential area.

Witnesses reported seeing pieces of the airplane separating during flight and the airplane in a rapid descent. Examination of the wreckage revealed that the outboard section of the right wing separated in flight, at a relatively low altitude, and then struck and severed portions of the empennage. There was no evidence of a preexisting mechanical anomaly that would have precluded normal operation of the airframe or engine.  

An examination of weather information revealed that numerous pilots reported icing conditions in the general area before and after the accident. At least three flight crews considered the icing "severe." Although severe icing was not forecasted, an Airmen's Meteorological Information (AIRMET) advisory included moderate icing at altitudes at which the accident pilot was flying. The pilot operating handbook warned that the airplane was not certificated for flight in severe icing conditions and that, if encountered, the pilot must exit severe icing immediately by changing altitude or routing. Although the pilot was coordinating for a higher altitude with the air traffic controller at the time of the icing encounter, it is likely that he either did not know the severity of the icing or he was reluctant to exercise his command authority in order to immediately exit the icing conditions. 

The National Transportation Safety Board determines the probable cause(s) of this accident to be: The airplane’s encounter with unforecasted severe icing conditions that were characterized by high ice accretion rates and the pilot's failure to use his command authority to depart the icing conditions in an expeditious manner, which resulted in a loss of airplane control.