The death toll from a Friday collision between a truck and an Amtrak train in Nevada has risen to at least six. Workers couldn't even enter the wreckage to retrieve bodies until Saturday afternoon because the passenger cars were so badly-burned and tilted. Twenty-eight people still remain unaccounted for, though the National Transportation Safety Board said some of the 210 with tickets might have gotten off the train before the crash. Emergency workers continue to look for bodies among the wreckage of the California-bound train, though the severe damage hampered their efforts to confirm a death toll. Investigators said visibility was excellent the day of the crash, and they said they don't know why the head driver didn’t stop when he saw the train approaching. The engineer, who survived the crash, also tried to bring the train to a halt. The truck was dragged half a mile down the tracks before a fire broke out in two of the passenger cars.