MANKATO — Six cars of a Union Pacific train that was heading to St. Paul went off the tracks in Mankato early Thursday.

The train was not carrying hazardous materials and there were no injuries when the derailment happened about 2:30 a.m.

Union Pacific spokesman Mark Davis said the derailment happened after the train struck a car from a Canadian Pacific train that was crossing in front of it. It was not clear why the Union Pacific train didn’t stop.

Rail authorities were investigating.

The derailment involved three Union Pacific engine cars and three cars carrying grain. Davis said there was a small diesel fuel leak in the first engine, but the spilled fuel was being collected.

Davis said four Canadian Pacific train cars also derailed, but appeared to remain upright.

About 500 feet of track was damaged and will need to be replaced, Davis said.

Some grain may have spilled, but was cleaned up.