A National Weather Service team headed to western North Dakota on Tuesday to assess the strength of a tornado that injured nine people, one critically, and destroyed at least eight trailers at a workers' camp in the heart of the state's booming oil patch.

The twister touched down at 7:50 p.m. Monday at a camp just south of Watford City, about 30 miles southeast of Williston.

McKenzie County Emergency Management Director Jerry Samuelson said crews sifted through debris at the camp, and that he was confident nobody was missing. He said the situation would have been much worse had the tornado struck a few days earlier when there were many more trailers at the camp.

"Obviously, we're very fortunate there are no deaths, to our knowledge," Samuelson said.

Weather service meteorologist Todd Hamilton said two meteorologists and an emergency response specialist were leaving Bismarck at daybreak Tuesday to survey the damage at the camp. He said the agency should be able to rate the tornado on the enhanced Fujita scale later in the day.

"The only pictures we've seen, we're seeing some trailers moved around," Hamilton said. "You can't really discern that much from pictures."

It is likely that only one tornado touched down Monday night, although there were reports of several funnel clouds alongside baseball-sized hail, Hamilton said.

More storms were moving through the region early Tuesday but the chance of more tornadoes was small, Hamilton said.

Karen Holte, a volunteer at an American Red Cross shelter at Watford City's civic center, said the tornado descended so quickly that nobody had time to take shelter. Samuelson said all the injured had been inside their trailers.

The critically injured person was taken to Trinity Health hospital in Minot for treatment, Samuelson said. The others were treated at McKenzie County Memorial Hospital in Watford City.

Tony Beyda, who suffered a head wound and cuts on his arm, said he saw something flying toward him as the twister slammed into his home. He pulled back the bandage on his forehead to show how the skin had been stapled back onto his head.

"It peeled it back pretty good," he said.

William Bunkel, a trucker, was in Watford City when the storm hit. Bunkel, 38, said he had just moved his vehicle inside because of large hail when he spotted the funnel cloud in the distance. He estimated it stayed on the ground for about a minute.

"We saw it form, come out of the sky, hit the ground and go back up into the clouds," he said.

The oil boom has brought tens of thousands of people into the area looking for work. Many live in hastily assembled trailer parks, also known as man camps, housing pre-fabricated structures that resemble military barracks. Some companies rent blocks of hotel rooms for employees to live in, and some workers sleep in their cars or even tents.

Housing developments are constantly popping up but the developments are not keeping pace with demand and oil money has pushed rents to among the highest in the nation: A simple one bedroom apartment in Williston can easily cost $2,000 per month in rent. Even a spot to park a trailer can cost over $800 per month.

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Associated Press writers Blake Nicholson in Bismarck and Carson Walker in Sioux Falls, South Dakota, contributed to this report.

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