The Transportation Safety Board of Canada said an Oklahoma-bound train derailed Dec. 9 in a remote area of Saskatchewan, releasing about 9,500 barrels of petroleum products onto the ground and into the air.

The Canadian Pacific Railway Ltd. train originated near Hardisty, Alberta, in Canada's oil sands region and was headed to Stroud, Okla., which is about 55 miles southwest of Tulsa. A total of 33 tank cars derailed just after midnight CT, of which 20 lost their loads, the agency said. There were no injuries in the incident and an estimated 1.5 million liters of petroleum products were spilled.

"The head-end 23 tank cars derailed east of the crossing and came to rest in various positions in a large pile over a distance of approximately 500 feet," the Transportation Safety Board said in an incident update. "About 20 of the 23 tank cars sustained breaches, released product and became engulfed in a large pool fire which burned for approximately 24 hours."

Trains originating near Hardisty, where Canada's biggest midstream companies have terminals, are generally carrying diluted bitumen, a mixture of tar-like heavy oil and condensate. Condensate is an highly combustible NGL similar to gasoline. The Transportation Safety Board said it had dispatched six investigators to the scene as of Dec. 12. The Canadian Press reported that more than 100 fire, cleanup and other workers were at the site a day after the incident.

Of the derailed tankers nine were Class 117R cars, a newer design known as DOT-117 in the U.S. that was introduced after a 2013 derailment in Lac-Megantic, Quebec which left 47 people either burned to death or presumed dead. The remaining tank cars were CPC-1232, or DOT-111, which are slated to be out of service or rebuilt by 2025.

The Transportation Safety Board said no waterways appeared to have been affected by the incident. It plans to update the volume of liquids spilled and the possible cause of the accident as the investigation progresses.