The crude oil carried in tankers that derailed and ignited in Lac-Mégantic in July was misclassified as a less volatile substance, the Transportation Safety Board of Canada announced this morning.


At a news conference in Ottawa, the lead investigator on the rail disaster in Lac-Mégantic, Donald Ross, said that misclassification, "explains in part why the crude ignited so quickly once the train cars were breached."


The revelation comes after tests were conducted on oil contained in nine train cars that did not derail or catch fire in incident.


The 78-car, unmanned train rolled down an incline into the core of the town, left the tracks and exploded early in the morning on July 6. The blast and fires killed 47 people and destroyed several blocks neighbouring the train tracks.


The TSB said it was immediately issuing safety advisory letters to rail authorities in Canada and the U.S., where the train originated, to review the processes for suppliers and companies transporting dangerous goods to ensure the description of the products are accurate and documented properly.


The crude oil in the Montreal, Maine & Atlantic train that derailed in Quebec had been listed as packing group three, the least hazardous on the scale.


The oil actually had the properites of a class two substance, which also includes goods like gasoline, that have a lower flash point and will therefore ignite quicker.