WATFORD CITY, N.D. — A tornado struck a workers camp in North Dakota’s oil patch on Monday, injuring nine people, including one critically, and destroying eight trailers where workers had been living, an emergency management official said.

The twister touched down at around 7:50 p.m. at a camp about 5 miles south of Watford City, the National Weather Service reported. Watford City is in the west of the state and about 30 miles southeast of Williston, the city at the heart of the state’s oil boom.

McKenzie County Emergency Management Director Jerry Samuelson said the crews were sifting through a large amount of debris at the camp, but that he was confident that nobody was missing. He said there were a lot more trailers at the camp just a few days ago, so the situation could have been a lot worse had it happened earlier.

“Obviously, we’re very fortunate there are no deaths, to our knowledge,” Samuelson said.

The critically injured person was taken to a hospital in Minot for treatment, he said. The others who were hurt were treated at McKenzie County Memorial Hospital in Watford City.

The American Red Cross said it was setting up a shelter in the civic center in Watford City with 40 beds.

William Bunkel, who works for a trucking company, told The Associated Press late Monday that he was in Watford City with some co-workers when the tornado warning came. They had just moved their vehicles inside because of large hail when they spotted the funnel cloud.

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

Bunkel, 38, took photos of the twister and estimated that it remained on the ground for nearly a minute. He said he couldn’t see any debris.

“It was a little bit too far away. We just saw the clouds and the rotation,” he said.

The oil boom has fueled a population boom for the area, bringing in tens of thousands of people looking for work. Many live in hastily-assembled trailer parks or man camps, which contain pre-fabricated structures that can 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 in big areas of town that didn’t exist on maps a couple of years ago. But they are still not enough to keep 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.