Government regulators defended their record on moving hazardous materials by rail, noting that 2012 was the safest year in the industry's history. But oil trains have bucked that trend, thanks in part to the massive amount of oil being moved out of western North Dakota, where the industry's rapid growth is far outpacing pipeline development.
No one was hurt when the mile-long BNSF Railway train derailed Monday afternoon near the eastern North Dakota town of Casselton, but the overturned tankers - exploding and engulfed in plumes of flames and black smoke for more than 24 hours - burned so hot that emergency crews didn't even attempt to put out the blaze. Most of Casselton's roughly 2,400 residents agreed to temporarily evacuate due to concerns about unsafe air.
"This is too close for comfort," Casselton Mayor Ed McConnell said Tuesday.
While the overall rate of oil train accidents remains low - less than 0.1 percent of crude-carrying tank cars have suffered accidental releases this year - there's been a sharp increase in the number of releases over the past several years. That's driven by a surge in drilling for unconventional shale oil in North Dakota and other western states.
Through early November, the most recent data available, crude releases have been reported from 137 rail cars in 2013, according to an Associated Press analysis of federal accident records. By comparison, only one release was reported in 2009, before the boom got well underway.
The rail tracks in eastern North Dakota run through the middle of Casselton, about 25 miles west of Fargo. McConnell estimated that dozens of people could have been killed if the derailments had happened within the town.
The mayor said it was time to "have a conversation" with federal lawmakers about the dangers of transporting oil by rail.
"There have been numerous derailments in this area," he told the AP. "It's almost gotten to the point that it looks like not if we're going to have an accident, it's when."
Gov. Jack Dalrymple visited Casselton, his hometown, to view the scene. He called it a "major catastrophe" that would prompt concern no matter where it happened.
"People will be asking a lot of questions about the safety of equipment, the safety of railroad operations, and why did the derailment occur in the first place," Dalrymple said.
The National Transportation Safety Board, which is heading the investigation, said it would examine the train recorder, the signal system, the condition of the train operators, train and tracks, as well as the response to the derailment.
NTSB member Robert Sumwalt said the tankers involved were older-model DOT-111s, which have shown a tendency to rupture in other accidents. Tank car makers have been rebuilding the DOT-111, the workhorse of the oil-by-rail industry, to tougher safety standards since a 2009 crash of an ethanol train near Rockford, Ill., but most of the nation's fleet has not yet been retrofitted.
Sumwalt said a westbound BNSF train carrying grain derailed first, and a portion of it fell onto an adjacent track carrying the eastbound BNSF oil train. Sumwalt said both lead locomotives of the 106-car train were destroyed. BNSF spokeswoman Amy McBeth said 18 cars on the oil train derailed and burned.
Officials canceled the town's voluntary evacuation recommendation Tuesday afternoon after air quality tests, and a Red Cross shelter set up at the high school was shut down.
Government regulators noted their record on moving hazardous materials by rail, saying they've conducted unannounced spot inspections to make sure crude oil is being properly handled, issued rail safety advisories and worked to update regulations including for the DOT-111s.
Federal Railroad Administration Associate Administrator Kevin Thompson added that 2012 was the safest year in the industry's history and that hazardous material releases are down 16 percent over the last decade, despite the uptick in oil train accidents.
Those accidents include the Nov. 8 derailment of more than two dozen crude oil cars into an Alabama swamp that released almost 750,000 gallons of crude and led to another fiery explosion, but again no injuries.
And the U.S. Department of Transportation data analyzed by AP does not include a July oil train accident in Quebec in which 47 people were killed when a shipment of North Dakota oil derailed in the town of Lac Megantic.
The Casselton derailment comes just days after North Dakota's top oil regulator, Lynn Helms, told state lawmakers that his agency was considering crafting a report "to dispel this myth that it is somehow an explosive, really dangerous thing to have traveling up and down rail lines."
Wayde Schafer, a North Dakota spokesman for the Sierra Club, has predicted such catastrophes since crude began leaving the state by rail in 2008, when North Dakota reached its then-capacity for pipeline shipments.
"As if we needed another wake-up call after Quebec, here's another wake-up call," Schafer said.
Ron Ness, president of the North Dakota Petroleum Council, said the state's drillers increasingly are using trains to reach more lucrative markets because of the lack of pipelines and difficulty in securing permits for them.
Sheldon Lustig, a rail expert who consults with local governments on accidents and hazardous materials, said oil train explosions underscore that not enough is being done by either government or industry.
"The evidence speaks for itself," he said. "I've talked to some of the crews and they refer to them as 'bomb trains.' They are worried, especially in view of the volatility of the cargo being moved."
Federal officials have said they stepped up inspections of oil trains even before the Quebec accident. But Lustig said he's seen no evidence that any corrective measures were taken for whatever defects were discovered.___ Associated Press writers James MacPherson in Bismarck, North Dakota, and Dirk Lammers in Sioux Falls, South Dakota, contributed.