Investigators are trying to determine what caused a train to de-rail on a Mississippi River bridge in Clinton. Mark Davis is a spokesman for the Union Pacific Railroad headquartered in Omaha, Nebraska.Davis says the wheels apparently came off a car carrying soybean meal and the car dangled over the bridge. He says half the car’s load fell to the ground below. Davis doesn’t know why the wheels came off and the investigation could take a couple of days. Davis says the track was blocked for most of last night and into this morning.They had to find a crane that was heavy enough to lift the car back on the track and that was accomplished around nine o’clock. Davis says the accident caused quite a back up in rail traffic as it’s a very busy line that goes from Chicago all the way to the west coast. Davis says around 60 trains a day use the route and they had to be diverted to a different track. The trains are now moving along the line once again.