Last Updated Dec 31, 2013 5:00 PM EST
CASSELTON, N.D. -- Officials are lifting a recommended evacuation for residents of a small North Dakota town that's near the site of a fiery oil train derailment.
The 2,400 residents of Casselton were asked to leave Monday afternoon after a BNSF Railway train derailed about a mile from town. A series of explosions sent massive fireballs and a smoke plume into the air. Some cars were still burning a day later.
Cass County Commission Chairman Ken Pawluk says the evacuation recommendation is being lifted Tuesday afternoon.
But he says officials are urging residents south of the derailment to stay vigilant about changing conditions. Those directly within one mile south of the incident location are advised to use extra caution upon returning to their homes, reports CBS Fargo, N.D. affiliate KXJB-TV.
Pawluk estimated that the fire was about 80 to 90 percent burned out by Tuesday afternoon.
No injuries have been reported.The rail tracks run straight through the middle of Casselton, about 25 miles west of Fargo. Mayor Ed 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."
The derailment happened amid heightened concerns about the United States' increased reliance on rail to carry crude oil. This is the third major accident involving oil-carrying trains in recent months. Fears of catastrophic derailments were particularly stoked after last summer's crash in Quebec of a train carrying crude from North Dakota's Bakken oil patch. Forty-seven people died in the ensuing fire. In early November, portions of a 90-car oil train derailed in Alabama.
The explosions Monday afternoon sent flames and black smoke skyward outside of Casselton, about 25 miles west of Fargo. Investigators couldn't get close to the blaze and official estimates of how many train cars caught fire 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 it thought 10 cars were on fire.
The cars were still burning as darkness fell, and authorities said they would be allowed to burn out.
Crews from BNSF were conducting air monitoring tests to determine the level of contamination and when people could return to their homes, KXJB says.
Authorities hadn't yet been able to untangle exactly how the derailment happened, but a second train carrying grain was involved. BNSF spokeswoman Amy McBeth said the train carrying grain derailed first, then knocked several cars of the oil train off adjoining tracks.
BNSF said the trains had more than 100 cars each.
The National Transportation Safety Board said Monday night it has launched a "go-team" to investigate the accident.
Ryan Toop, who lives about a half-mile away, said he heard explosions and drove as close as about two city blocks to the fire, which erupted on a day when temperatures were below zero.
"I rolled down the window, and you could literally keep your hands warm," Toop said.
The tracks that the train was on pass through the middle of Casselton, and Cass County Sheriff's Sgt. Tara Morris said it was "a blessing it didn't happen within the city."
Morris said it could take up to 12 hours before authorities could get close to the fire. About 80 of the cars were moved from the site. Jeff Zent, a spokesman for Gov. Jack Dalrymple, said the National Guard was on alert if needed.
Temperatures were forecast to drop to minus 20 in Cass County overnight.
"Of course, Mother Nature, being North Dakota, it has to be one of the coldest nights of the year. It's deadly cold out there tonight," Laney said.
A shelter has been set up in Fargo. Casselton Mayor McConnell said he didn't want any residents sleeping in their vehicles.
"All the experts say it can be a hazardous situation to their health," McConnell said. "We're going to try to get everybody out of the town."
In the initial hours, authorities told residents to stay indoors to avoid the smoke.
Hannah Linnard, 13, said she was in the bedroom of her friend's house about half a mile from the derailment, wrapping late Christmas presents.
"I looked out the window and all of a sudden the train car tipped over and the whole thing was engulfed in flames and it just exploded. The oil car tipped over onto the grain car," she said. Hannah said she could feel the warmth even inside the house.
Terry Johnson, the manager of a grain dealer less than a mile from the derailment, said he heard at least six explosions in the two hours following the incident.
"It shook our building and there was a huge fireball," he said.
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.