No one was hurt in Monday's derailment of the mile-long train that sent a great fireball and plumes of black smoke skyward about a mile from the small town of Casselton. The fire had been so intense as darkness fell that investigators couldn't get close enough to count the number of burning cars. The National Transportation Safety Board was preparing to investigate.
Most residents heeded a recommendation to evacuate their homes as strong winds blew potentially hazardous, acrid smoke toward the town overnight, Mayor Ed McConnell said early Tuesday.
"I drove in this morning and looked like most people had left. There weren't a lot of lights on," McConnell said.
The North Dakota Department of Health warned that exposure to burning crude could cause shortness of breath, coughing and itching and watery eyes. It had said those in the vicinity with respiratory conditions such as asthma, bronchitis or emphysema should minimize outdoor activity.
Health experts were testing the air quality.
"Is it highly hazardous or did most of it burn off in the fire?" Cass County Sheriff Paul Laney said of elements in burning crude that could be risky for health. "We just don't know."
Residents said the blasts endured for hours after the derailment, shaking their homes and businesses. Official estimates of the extent of the blaze varied. BNSF Railway Co. said it believed about 20 cars caught fire after its oil train left the tracks about 2:10 p.m. Monday. The sheriff's office said Monday it thought 10 cars were on fire. Officials said the cars would be allowed to burn out.
The rail tracks run straight through the middle of Casselton, a town of 2,400 people about 25 miles west of Fargo. McConnell estimated that dozens of people could have been killed if the derailments had happened within city limits. He said it is 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 Associated Press. "It's almost gotten to the point that it looks like not if we're going to have an accident, it's when. We dodged a bullet by having it out of town, but this is too close for comfort."
A train carrying crude from North Dakota's Bakken oil patch crashed in Quebec last summer and 47 people died in the ensuing fire.
North Dakota is the No. 2 oil-producing state in the U.S., trailing only Texas, and a growing amount of that is being shipped by rail. The state's top oil regulator said earlier this month that he expected as much as 90 percent of North Dakota's oil would be carried by train in 2014, up from the current 60 percent.
The number of crude oil carloads hauled by U.S. railroads surged from 10,840 in 2009 to a projected 400,000 this year. Despite the increase, the rate of accidents has stayed relatively steady. Railroads say 99.997 percent of hazardous materials shipments reach destinations safely.
Shipping oil by pipeline has to be a safer option, McConnell said Tuesday.
Authorities haven't yet been able to untangle exactly what caused the derailment. BNSF spokeswoman Amy McBeth said another train carrying grain derailed first, and that this knocked several cars of the oil train off adjoining tracks.
BNSF said both trains had more than 100 cars each.
The NTSB said Monday night it had launched a "go-team" to investigate this latest derailment.
The fire died down overnight, "but we've still got plenty of smoke and plenty of fire and plenty of heat," Sheriff's Deputy Joe Crawford said.
Jeff Zent, a spokesman for Gov. Jack Dalrymple, said the National Guard was on alert if needed.
Laney said much of Casselton's water tower was covered in soot and that he expects to see a lot of the black powder around town as the day progresses.
"Wait until you see the footprints in the snow later on," he said. "That's the stuff coming out of the sky."
Associated Press writers James MacPherson in Bismarck, N.D., and Dirk Lammers in Sioux Falls, S.D., contributed.