On July 6, 2013, shortly before 1:00 am, a Montreal, Maine & Atlantic Railway freight train which was parked for the night on a hill seven miles above Lac Megantic, Quebec started to roll. The unit train carrying approximately 48,000 barrels of crude oil produced from the Bakken oil fields in North Dakota in 78 DOT Class III tank cars reached a speed of 65 mph and 63 of the tank cars derailed in the centre of the Town, spilling approximately 37,000 barrels of crude oil and causing fires and explosions which destroyed 40 buildings, 53 vehicles and killed 47 people, many of whom were relaxing in bars and restaurants in Lac Megantic's scenic downtown on a warm summer evening.

On August 19, 2014, the Transportation Safety Board of Canada (TSB) released its 181 page report of its investigation of the tragedy. The TSB, like the National Transportation Safety Board in the united States, investigates transportation safety. It is not a function of the TSB to assign fault or determine civil or criminal liability.

The TSB found that the accident in Lac Megantic was due to 18 human and mechanical causes, including improper application of the brakes on the parked train, ineffective training and oversight by the rail company and poor regulatory oversight by Transport Canada. In its investigation, the TSB considered the volatility and flammability of the crude oil cargo, including how it was characterized, documented and handled for the purpose of transportation of dangerous goods laws.

Some public commentary after the disaster suggested that as some Bakken crude oil was produced through the hydraulic fracturing of wells, that hydraulic fracturing fluids in the crude oil in the tank cars contributed to the scope of the disaster.

The TSB considered this possibility but dismissed it. The TSB said after examining the properties of the crude oil that: "There was no indication that the crude oil's properties had been affected by contamination from fracturing process fluid additives."

Review a copy of the TSB's report.