Arvydas KniukA!ta/iStockphoto/Thinkstock

The investigation into the train crash in Lac-Megantic, Quebec, has revealed that the crude oil transported in the railcars had a lower flash point than indicated on documents, meaning that it was actually more volatile than could be expected, the Transportation Safety Board of Canada has announced.

Mislabeling the crude as a less flammable substance may not have been the direct cause of the disaster but it raises further questions regarding the effectiveness of crude transportation oversight in Canada, the Wall Street Journal reported.

The Transportation Safety Board of Canada said it had sent a letter to regulators in Canada and the United States, calling for an immediate revision of labeling procedures for shipping hazardous materials. The U.S. Pipeline and Hazardous Materials Safety Administration has already started looking into proposals that could improve rail safety by making tank cars more puncture-resistant.

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Investigators think that because of the mislabeling error, crude oil may have been carried by railcars that did not meet the requirements for safe shipment. Although they have not completed their investigation, they believe that the mistake explains why the derailed train exploded. Crude oil typically ignites at very high temperatures and would not explode in an incident like the one in Lac-Megantic, the Wall Street Journal noted.

According to Donald Ross, leader of the Canadian investigation team, tests to identify the actual product carried by the train from North Dakota to the east coast of Canada will continue.