(AP) — At least 10 times since 2008, freight trains hauling oil across North America have derailed and spilled significant quantities of crude. Most of the accidents have touched off fires or catastrophic explosions.

The derailments released a total of almost 3 million gallons of oil, and the deadliest wreck killed 47 people in the town of Lac-Megantic, Quebec.

Those findings are from an Associated Press review of U.S. and Canadian accident records. They underscore a lesser-known danger of America’s oil boom, which is changing the global energy balance but raising urgent safety questions closer to home.

Adding to the danger is the unusually high volatility of the light, sweet crude from the fast-growing Bakken oil patch in Montana and North Dakota, where many of the oil-hauling trains originate.