July 8, 2013 9:30 AM, EDT

Derailment of Freight Train Carrying Crude Oil Causes Huge Explosion in Quebec

Rescuers continued searching Monday for about 40 people missing after a huge weekend freight train crash in Quebec in which at least five railcars loaded with crude oil exploded after becoming untethered, the Associated Press reported.

Saturday’s accident near the town of Lac-Mégantic, which killed at least five people, happened after all but one of the train’s 73 tanker cars came loose and sped downhill for about seven miles before derailing and exploding, AP reported.

Canadian Prime Minister Stephen Harper, who on Sunday visited the town about 150 miles east of Montreal and 10 miles from the Maine border, likened the scene to a “war zone,” the New York Times reported.

The oil was being transported from North Dakota’s Bakken oil region to a refinery in New Brunswick, Canada. Because of limited pipeline capacity in the Bakken region and in Canada, oil producers are increasingly using railroads to transport oil to refineries, AP said.

The Canadian Railway Association has estimated that as many as 140,000 carloads of crude oil will be shipped on Canada’s tracks this year — up from 500 carloads in 2009, AP reported.

The Quebec disaster is the fourth freight train accident involving crude oil shipments in Canada under investigation since the beginning of the year, AP reported.