Casselton, ND, Evacuation Order Lifted After Fiery Train Collision Fears of a toxic plume prompted evacuation of Casselton, N.D., residents.

Dec. 31, 2013 -- A recommended evacuation order was lifted this afternoon for residents of a small North Dakota town, one day after a mile-long train carrying crude oil collided with another train, triggering a series of thunderous explosions and sending toxic fumes into the air.

Officials from state environmental and health departments tested the air within the town of Casselton and determined it was safe for residents to return to their homes, according to a statement from the Cass County Sheriff's Office.

Casselton's 2,400 residents were warned that "small flare-ups or smoke clouds" may result when train cars are being moved and were asked by the sheriff's office to "keep a respectful distance."

About 65 percent of residents had evacuated the area as of Monday night, according to the Cass County Sheriff's Office.

The main concern for residents' safety was related to the fumes from the fire, Cass County Sheriff's spokeswoman Sgt. Tara Morris said.

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People who have respiratory conditions such as asthma, emphysema or bronchitis were strongly urged to stay inside or evacuate the town.

"Crude oil, as it burns, has a lot of particulate matter in it, lot of fumes and other bad things that are really bad for people, especially those with respiratory illnesses," Dr. John Baird of Fargo-Cass Public Health said.

No injuries were reported as a result of the collision.

Authorities said they would let the fires burn, hoping some of the oil would burn off and make the job for firefighters easier, Sheriff's spokeswoman Morris said.

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Federal officials are on the scene investigating the crash. A train carrying grain derailed first, and then knocked several cars of its crude oil train off adjoining tracks, BNSF Railway Co. spokeswoman Amy McBeth said.

Video taken three-quarters of a mile away captured the moment one of the train cars exploded. A mushroom cloud of fire blasted into the sky and then black smoke smothered the surrounding area as the wreckage continued to burn. The flames created dark clouds that could be seen for 15 miles.

"It was almost like nighttime," eyewitness Loren Parks said. "It was just dark. The entire sky is just blacked out, you can't see anything."

There were 112 cars in the westbound grain train and 106 cars in the eastbound crude oil train, according to BNSF. The majority of train cars were not derailed and pulled away from the derailment location.

Only 20 people have gathered at a middle school in Fargo, which has been turned into a shelter, Sheriff's spokeswoman Morris said. Evacuations for residents of Casselton will remain voluntary, she added.

This explosion is the third accident in the past six months involving trains transporting North Dakota crude oil. No injuries or deaths were reported when a 90-car train derailed in rural Alabama in November, but the aftermath is still being cleaned up.

In July, an oil train derailment in Quebec killed nearly 50 people.