Norfolk Southern spokesman Rick Harris said the cause of the 6 a.m. accident has not been determined yet. King Mill Road remains blocked. "We're looking to clean up debris and repair the track," he said. There are no estimates as to when those tasks will be completed, he said. Other trains are being rerouted over the company's north-south Griffin line and a CSX line. Harris said 20 cars were derailed, out of 137 cars and three locomotives on the northbound train which departed Macon and was bound for the railway's Linwood, N.C., train yard. The derailed cars included seven that carried wood pulp, rock and lumber.