CP said in a statement there were no injuries to the crew, no public safety issues and no dangerous goods involved.
The west-bound train derailed at about 2 a.m. MT. The 16 cars contained grain and concrete, CP said.
The derailment "did impact a small, low-level railway bridge."
Canadian Pacific crews have been deployed to the scene, and will consult with Parks Canada about any environmental issues.
The Transportation Safety Board of Canada has also sent a team of investigators.
"CP's emergency protocols were immediately enacted and all safety precautions and measures are being taken as our crews respond to the situation with local officials," the statement said.