The fiery derailment of an oil train in Alabama is raising new concerns about the danger of transporting crude, particularly oil from the Bakken fields of the United States and Canada.

A 90-car train loaded with crude derailed early Friday in rural Alabama, causing 11 cars to erupt in flames. Witnesses reported several explosions and flames that reached as high as about 90 metres in the air. There were no injuries.

State officials said the oil originated from North Dakota's Bakken fields, which were also the source of the crude that exploded during a derailment in Lac-Mégantic, Que. That July 6 derailment killed 47 people after a train carrying 72 cars, and operated by Montreal, Maine & Atlantic Railway, crashed in the centre of the town, razing the downtown.

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Questions are being raised about the growing practice of moving oil by rail, particularly from the Bakken region, where the crude is thought to be more explosive than transporters and oil producers previously believed.

Amended documents filed in Quebec provincial court this week in a class-action lawsuit allege that oil companies, in addition to railways and fuel brokers shipping the crude, should have known the oil in the Lac-Mégantic tragedy was far more volatile than other forms of crude oil. The lawsuit, which has yet to be certified, has been launched on behalf of several Lac-Mégantic victims.

The amendment names U.S. energy producers Marathon Oil of Houston and Slawson Exploration of Wichita, Kan., alleging both companies were "responsible for determining the hazard class of the hazardous materials … However, from the point of extraction to the point of explosion in Lac-Mégantic, these risks were inadequately signaled and inadequate precautions were taken to ensure safe transport."

Shipments of oil by rail have risen sharply in the past few years, as crude production booms in regions like North Dakota, where there is limited pipeline capacity. In Canada, crude oil shipments have risen from a few hundred in 2009, to roughly 140,000 in 2013. Similarly, in the U.S., crude oil shipments by rail have risen more than 400 per cent since 2005.

Crude from the Bakken shale formation, which straddles North Dakota, along with parts of southern Manitoba and Saskatchewan, is considered lighter than other forms of oil from Alberta and Texas, and requires less refining.

However, the lighter elements of the crude, and the vapours they give off, have raised concerns as to whether the oil is more explosive.

"Bakken oil production yields not only highly sought after crude oil, but also a significant amount of volatile vapours, gases and light liquids, including propane, butane, pentane and natural gasoline," the court documents filed in Quebec say. "When left in their combined state, these gases and liquids can become extremely explosive, even at relatively low ambient temperatures. Some of these gases may be burned off – or flared off – at the well head, but others remain in the extracted well product."