A train carrying crude oil that derailed, exploded and killed 47 people in a Quebec town in July 2013 traveled through Chicago, Detroit, Minneapolis, Milwaukee and North Dakota before the accident, a report from Canada's Transportation Safety Board said.

Canada's federal transportation regulator blamed "systemic problems" for the incident in Lac-Megantic, Quebec, a catastrophe that sounded alarms about the soaring amounts of crude oil traveling by railroad across North America.

“Accidents never come down to a single individual, a single action or a single factor. You have to look at the whole context,” Transportation Safety Board Chairwoman Wendy Tadros said. “In our investigation, we found 18 factors played a role in this accident."

About 1.6 million gallons of crude oil spilled when five cars derailed, the report said. In addition to killing 47 people, fires and explosions destroyed 40 buildings, 53 vehicles and rail tracks, and the crude contaminated a nearby river and lake as well as the downtown.

The disaster, as well as a handful of derailments and explosions in the United States, sparked fresh congressional scrutiny of rail safety for shipping crude oil unlocked through hydraulic fracturing, or fracking.

The number of carloads of crude originating from the Bakken shale formation in North Dakota and Montana, which now produces 1 million barrels of oil per day, has jumped from 10,800 per day in 2009 to more than 400,000 last year, according to the U.S. Department of Transportation. Accidents involving trains carrying crude oil have increased as well, climbing from zero in 2010 to five both last year and this year. DOT predicted derailments would rise to 15 next year absent new safeguards, dropping to five annually by 2034.

Concern about future crashes pushed the Obama administration to offer draft rules last month ahead of schedule. The proposed standards would phase out old tankers unless updated with new safety features, impose speed restrictions, and require carriers to use the safest possible routes.

The Transportation Department offered a mix of proposals for comment, with the price tag between 2015 and 2034 ranging from a low of $1.7 billion of benefits at a $2.6 billion cost to $4.75 billion of benefits and $6 billion in costs. The DOT's Pipelines and Hazardous Materials Safety Administration is also looking into whether crude oil from the Bakken shale formation is more flammable than other varieties.