Canadian Pacific Railway Ltd said five tankers containing oil derailed on Tuesday morning near Jansen, Saskatchewan, and one of the cars is leaking crude, the third spill for the company in two months.
Ed Greenberg, a spokesman for Canada's No.2 railway, said the cars containing Western Canadian crude were on an eastbound mixed-freight train. The company does not yet know how much spilled from the leaking tanker, but Greenberg said the oil has been contained at the site of the derailment.
"One of the cars did leak some product but there is no assessment of how much escaped," he said.
The derailment, which is being investigated by Canada's Transportation safety board, comes after one of CP's trains derailed near Parkers Prairie, Minnesota, in late March, spilling 360 barrels of Canadian crude.
A second, 400-barrel spill came less than a week later when a train carrying crude tankers and other freight cars derailed in northern Ontario.
A boom in North American oil production has prompted a huge rise in crude-by-rail transport as output has outgrown the existing pipeline network. The spill may again prompt concerns about the environmental risks of shipping crude on railways.
Hunter Harrison, the railway's chief executive, said earlier this month that CP was investing in new technology to limit derailments on the company's rail network in Canada and the United States.
The company does not yet know when the line will be returned to service. Greenberg said trains can be rerouted around the derailment.
Jansen is 148 kilometers (92 miles) southeast of Saskatoon, Saskatchewan.
CP shares were down C$1.57 to C$140.85 by midday on the Toronto Stock Exchange.