Crews cleaned up a mess of metal at the CN Symington rail yards in southeast Winnipeg, after about 25 CN rail cars derailed early Tuesday morning while they were being switched to various tracks.

CN spokesman Jim Feeny said Tuesday that investigators were trying to determine the cause of the accident, which took place shortly after midnight on Tuesday.

"There were no injuries and no environmental issues. The cars that derailed were mostly empty automobile carriers. There was one loaded automobile carrier, three loaded lumber cars and one empty tanker that were also involved," Feeny said.

He said the total dollar value of the damaged rail cars was not yet known.