Union Pacific spokesman Mark Davis says the train was going from Milwaukee to Chicago when 10 cars derailed around 9 a.m. Sunday.
Davis tells WISN-TV that six cars contained ash, three contained clay and one car was empty. Nothing spilled and there were no injuries.
Crews are working at the scene to make any repairs and get the cars back on the tracks.
Davis says about 12 Union Pacific freight trains travel the same route every day. Other trains will be rerouted or delayed while crews clear the scene.