Canadian officials say the oil carried by the train that derailed in July in Lac-Megantic, Quebec, flattening the town center and killing 47 people, was mislabeled as being less volatile than it actually was.
In a press release Wednesday morning, Canada's Transportation Safety Board said it had analyzed oil from a part of the 72-car train that didn't explode and found it had the characteristics of a Packing Group II product. However, the oil -- which came from North Dakota -- had been labeled as a Packing Group III product when it was loaded onto the train.
While both groups are considered "dangerous goods," Packing Group II includes liquids like gasoline that explode at a lower temperature than Packing Group III.
The fact the oil was mislabeled "explains in part why the crude ignited so quickly once the train cars were breached," the Transportation Safety Board statement said.
Officials said it's unclear why the crude oil was mislabeled but pointed to inconsistencies in the way North Dakota suppliers and shippers classify hazardous products, according to The Globe and Mail.
Ultimately, however, investigators said that oil and gas company Irving Oil, which operates the New Brunswick refinery where the crude was headed, was responsible for how the product was labeled, according to The Toronto Star.
Lead investigator Donald Ross said that proper labeling of the products would not have affected the firefighters' response and possibly not even the tankers used to ship the products, The Canadian Broadcasting Company reports.
The country's government transportation agency, Transport Canada, said shortly after the disaster that there are no rules against leaving an unlocked, unmanned, running locomotive and its flammable cargo on a main rail line uphill from a populated area, The Associated Press reported in July.
The Lac Megantic tragedy occurred around 1 a.m. on Saturday, July 6, 2013, when firefighters in Nantes, Quebec, were called to extinguish a small fire on the 72-car train. As standard operating procedure, the firefighters turned the train off while putting out the fire, disabling the train's air-braking system. The unmanned train then rolled about 7 miles downhill and reached speeds over 60 mph before it jumped the tracks in the middle of the small, tourist town of Lac-Megantic about 18 minutes later. Part of the train exploded, incinerating about 30 buildings and killing 47 people, some of whom were burned beyond recognition.
The Transportation Safety Board says its investigation is ongoing. An Irving Oil spokeswoman told The Huffington Post that the company is cooperating with the investigation but did not offer further comment.