The accident happened as the Canadian Pacific Rail (TSX:CP) eastbound train was rolling through an area near the village of Jansen, about 150 kilometres southeast of Saskatoon.
The company said five cars derailed, but only one leaked its contents. A total of 575 barrels hit the ground, said spokesman Ed Greenberg.
"There is one car that was leaking product," Greenberg said. "It has been contained into the area around the car."
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The leaking car was well back in the 64-unit train and remained upright. The other four cars were on their sides.
Excavation equipment was being sent to the site to build a wall of dirt to further contain the spill.
Reeve Bruce Elke with the rural municipality of Jansen was content with the way the situation was being handled, although he noted he was seeding his farmland and had not been to the scene.
"My understanding was that it wasn't that big a spill and everything is going well," Elke said.
Oilspills of any sort have been increasingly under the microscope as debate rages over how best to get Canadian oil to foreign markets.
CP Rail has been increasing crude shipments as production ramps up from the oilsands and pipeline companies struggle to increase capacity quickly. Canadian National Railway (TSX:CNR) moved more than 30,000 carloads of crude to various North American markets last year and believes it can double that business in 2013.
However, in New York earlier this month, Prime Minister Stephen Harper suggested rail was a riskier way to go while stumping for U.S. approval of the Keystone XL pipeline from Alberta to the Gulf Coast.
Tuesday's spill marked at least the third involving a CP train in the last few months.
In April, about 20 freight cars, including two that were carrying light sweet crude oil, went off the tracks near White River, Ont., about halfway between Thunder Bay and Sault Ste. Marie. While it was initially thought that only 630 litres of oil leaked, the total was revised to about 63,000 litres.
In March, a Canadian Pacifictrain derailed in Minnesota. At the time, Minnesota Pollution Control Agency said 76,000 litres leaked onto the still-frozen ground.
In January a Canadian National train collided with a road grader near the community of Paynton in Saskatchewan. Police said at the time that about 1,000 litres of oil leaked from two tankers in that crash.
Greenberg said the train that detailed Tuesday was carrying other products besides oil, but there was no indication they were hazardous.
"It was a mixed freight train, so there were other rail cars with other commodities on it."
Firefighters from Jansen were called in as a precaution.
The Transportation Safety Board of Canada was sending an investigator to the site.