There were no injuries reported and there are no public safety concerns, CP Rail said.
The cause of the derailment in the western Canadian province is under investigation, the company said.
"CP personnel have responded to the scene and recovery operations are under way," the company said in a statement.
Canada is the world's biggest producer of potash, a key ingredient for producing nitrogen-containing fertilizers, followed by Russia and Belarus.
Potash prices have soared in recent months as Belarus, Russia's ally, became subject to sanctions by Western countries.
Canada depends heavily on its rail system to move commodities and manufactured goods to ports.