The flight was issued an instrument flight clearance with a cruise altitude of 8000 feet. The flight was uneventful until the pilot started his letdown and approach to the destination airport. As the flight descended from the assigned cruise altitude, the pilot reported to air traffic control that one engine had quit. A minute later the pilot reported that the second engine had also quit. The ATC controller continued to provide radar service until all contact was lost. The airplane was next observed by a witness who reported seeing fuel coming from the airplane. The airplane collided with the roadway and skidded about 500 feet, collided with a utility pole and burned. The fire destroyed the center section of the airframe, but the wreckage examination disclosed that the fuel selectors were in the auxiliary positions. According to the owner's manual, the fuel selectors should be placed in the main position for landings and takeoffs. The manual also states that fuel will vent from the main fuel tanks when there is insufficient space in the main fuel tank for returned fuel and vapors. The wreckage examination failed to disclose any mechanical malfunctions.