Three cars that derailed from a freight train north of Dubuque, Iowa, were lying on the frozen Mississippi River on Thursday, one of them having spilled some ethanol fuel, Canadian Pacific (CP) railway said. Thirteen cars and two engines remain off the tracks after the derailment on Wednesday, with two put back on the tracks, the company said in a statement. All fires in the cars have burned out, it said. The company said it wasn’t sure how much ethanol had leaked. A spokesman for the Iowa Department of Natural Resources said state officials are not sure if ethanol is leaking from the car. “We take our commitment to the environment very seriously, and are closely monitoring the impact at the site as well as downstream to determine what remediation will be needed,” the company statement said. The company said it is working closely the Iowa Department of Natural Resources, U.S. Fish & Wildlife, and the U.S. Environmental Protection Agency in monitoring efforts. “We have established 40 separate monitoring sites at 1-mile increments for 10 miles down the river (originally communicated as 10 sites total) downriver that will be able to detect the presence of ethanol in the water, as well as the level of dissolved oxygen,” the statement said..