The aircraft was on an IFR flight from Memphis, TN to Selma, AL. During arrival, he was cleared for an NDB approach to the Craig Airport. At that time, the weather was reported as measured 400 ft overcast, visibility 1/2 mi with fog. The weather minimums for the approach were 700 ft ceiling, 3/4 mi visibility. The pilot reported that he was going to try the approach, and if he did not make it, he would go to Montgomery, AL. The controller lost contact with the aircraft after the approach was started (at dusk). A witness reported seeing the aircraft before it crashed. He stated that he saw the aircraft bank to miss a 50 ft tree, then disappear into the fog. This witness estimated that the ceiling and visibility were both about 100 ft. Two mercury vapor security lights were installed on the farm where the plane crashed. They were located between the final approach fix and the runway. An examination of the wreckage did not reveal any preimpact aircraft malfunctions.