Two freight trains collided early Wednesday, derailing 40 cars and sending an engine and some railcars plunging into the Mississippi River, authorities said. No serious injuries were reported.

Why the Canadian-Pacific trains collided is under investigation, said Mike LoVecchio, a spokesman for the rail company in Calgary, Alberta.

The trains crashed about 5:30 a.m. near Dresbach in southeastern Minnesota. One rail car struck a 1,000-gallon propane tank attached to a switching station, causing a small leak that was stopped by early afternoon, authorities said.

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About 25 disabled veterans at the nearby Mosher Veterans Rest Home near Dresbach were evacuated for several hours as a precaution because of the leak but returned home by late afternoon, said Joyce Tlougan, deputy director of Winona County Emergency Management.

One train engine was partially submerged in the Mississippi River, Tlougan said. It wasn't clear whether any of the cars contained hazardous materials or were leaking anything into the river, she said.

The railroad dispatched hazardous material professionals to the scene, LoVecchio said.

The locomotive that did not end up in the water was leaking diesel fuel but the fluid was contained on land, Tlougan said.

Four workers operated the two trains. Two were taken to a hospital as a precaution, but all four were "safe and accounted for," LoVecchio said.

The trains were traveling toward each other on the single tracks, although it's not clear why, Tlougan said.

LoVecchio said the line includes a "siding where one train would pass another," but he did not know what role, if any, that may have played in the crash.

The derailment disrupted Amtrak service to hundreds of passengers, said Bob Kamrowski, station manager in La Crosse, Wis. Amtrak makes two trips per day on the route blocked by the derailment.

People planning to board Amtrak trains Wednesday in several Minnesota and Wisconsin cities were being bused to either Chicago or Minneapolis, he said.

"They are telling me one day (of disruption)," Kamrowski said. "I have no idea if that is going to be the truth or not."

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