The railway says 15 cars carrying grains and fly ash, a material used to make concrete, went off the track west of the town early Friday morning.
A news release from the railway said there were no hazardous materials involved and no one was injured, but that the incident "did impact a small-low-level railway bridge and there are a few cars in the creek bed below the bridge."
The railway said some of the cars have been breached, and the company is working with Parks Canada and environmental crews on the cleanup.
Safety board spokesman John Cottreau said a number of the cars have landed in 40 Mile Creek, which flows into the Bow River about 200 metres downstream.
"Seven of them are in the water," Cottreau said. "The bridge is destroyed."
CP said in the release that environmental monitoring is taking place.
"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 release stated.
Alberta Environment and Sustainable Resource Development said its staff are also at the scene.
Katrina Bluetchen, a spokeswoman with the department, said staff were concerned that some of the fly ash could enter the creek.
"It could affect the pH of the creek," Bluetchen explained, noting it could also build up as sediment.
"We're still getting updates so it's a little difficult to say what the impact is."
Cottreau noted that neither the fly ash nor the grain, which he said were lentils, are classified as dangerous under the Dangerous Goods Act.
He said TSB staff are at the site collecting information for the investigation into the cause of the derailment.