THE AIRCRAFT CRASHED AND BURNED SHORTLY AFTER TAKING OFF IN DARKNESS ON AN IFR FLIGHT PLAN. THE WEATHER WAS REPORTED AS INDEFINITE CEILING, ZERO OBSCURATION, VISIBILITY 1/4 MI WITH FOG, WIND 120 DEG AT 5 KTS. A NUMBER OF WITNESSES HEARD THE AIRCRAFT, BOTH BEFORE AND AFTER TAKEOFF. THE CONSENSUS OF THEIR STATEMENTS INDICATED THAT ONE ENGINE LOST POWER WHILE THE OTHER CONTINUED RUNNING AT A HIGH POWER SETTING. AN INVESTIGATION REVEALED THAT AN INTENSE POSTCRASH FIRE HAD CONSUMED MOST OF THE AIRCRAFT. THERE WAS EVIDENCE THAT THE PLANE HAD CRASHED IN A STEEP NOSE DOWN, RIGHT WING LOW ATTITUDE AND DID NOT MOVE AFTER IMPACT. THE RIGHT PROPELLER WAS FOUND IN A FEATHERED POSITION. THE LEFT PROPELLER BLADES WERE CURLED AND TWISTED. BOTH ENGINES WERE DISASSEMBLE, BUT NO EVIDENCE OF A MECHANICAL FAILURE WAS FOUND. THE GEAR AND FLAPS WERE RETRACTED AND THE COWL FLAPS WERE CLOSED.