The National Transportation Safety Board determines the probable cause(s) of this accident as follows.

A loss of power to both engines due to fuel contamination and, the pilot-in-command's failure to maintain an adequate airspeed during the subsequent emergency, which resulted in an inadvertent stall. Factors in the accident were: 1) the manufacturer's inadequate design of the airplane's fuel system, which does not facilitate fuel sampling during preflight inspections or routine normal maintenance; 2) the lack of a fuel drain valve in the fuel system for fuel sampling purposes.