A tornado injured nine people — one critically — and destroyed 15 trailers at a workers' camp in the heart of North Dakota's booming oil patch on Memorial Day Monday.

The person with critical injuries, 15-year-old girl, was flown to hospital in Minot. McKenzie County Emergency Manager Jerry Samuelson said Tuesday that he didn't know the nature of her injuries.

Samuelson said he did not know why the girl, whom he didn't name, was at the worker camp but that "families do live out there."

The other eight were treated at a local hospital for minor injuries and released.

The twister struck at about 7:50 p.m.

The camp, located about eight kilometres south of Watford City, which is in the west of the state about 48 kilometres southeast of the oil boom hub city of Williston, was quiet on Tuesday but the aftermath was clear.

Watford City tornado

This tornado near Watford City, N.D., on Monday evening was photographed by Kevin Ragan, an oil field worker who was staying at a worker camp nearby. His wife, who posted the photo on Twitter, said he's doing OK. (Kevin Ragan/Twitter)

Plywood and other debris was scattered across several hundred square feet. Four trailers and a couple of other prefabricated buildings were still standing.

It was cool and rainy at the site and there was very little activity. A heavily damaged truck was flipped over on the highway and several other abandoned vehicles were nearby. Road signs were flattened and tumbleweeds pushed up against some electrical wires.

A U.S. National Weather Service team is heading to western North Dakota to assess the strength of the tornado.

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

The situation could have been worse given that some worker camps in the county host hundreds of trailers, he said.

'Pure fear'

Dan Yorgason and his roommate were right in the middle of the tornado and started taking cellphone video as it passed over.

He said there was little warning that it was about the hit the trailer camp. They didn't even have time to get their shoes on before they ran to a truck.

"We didn't want to stay in our trailer, because, you know, I don't think a trailer's a very safe place to stay during a storm, you know how trailers are with tornadoes," he said.

"So we got in our pick-up truck with the thought of getting out of there but then we realized the tornado was coming down the only place we could escape to."

When the tornado reached the trailer park, it seemed to just stop and hover.

"It wasn't going anywhere, which scared us even more because we didn't know if it was going to start moving towards us or what it was going to do," Yorgason said.

In the video, he and his roommate can be heard laughing, but it wasn’t because they thought the situation was funny.

“That was pure fear and I just, it was, my adrenaline was really kicked up and I was scared to death, you know? I have a wife and I have kids and I didn't want to die,” Yorgason said.

“But I realized it was very possible."

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.

The oil boom has led to a population explosion in western North Dakota, bringing in tens of thousands of people looking for work.

Many reside in hastily-assembled trailer parks or man camps, which contain prefabricated 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 a month in rent.

Even a spot to park a trailer can cost over $800 per month.

Storm hits southwest Manitoba

The same weather system brought thunderstorms to parts of southwestern Manitoba on Monday evening.

Hail in Melita

Hail in Melita, Man., on Monday evening. The same weather system that produced the tornado in North Dakota brought thunderstorms to parts of southwestern Manitoba on Monday evening. (Brett Laboss/Twitter)

Environment Canada issued a severe thunderstorm warning for the Melita, Boissevain, and the Turtle Mountain Provincial Park areas.

The storm hit Melita just after 9 p.m., following a drastic drop in temperature that went from 23 C at 8 p.m. to 14 C at 9 p.m.

That area, about 300 kilometres northeast of Watford City, was pummelled by 28.6 millimetres of rain and loonie-size hail that piled up to 15 centimetres deep in places.

The winds also gusted to 70 km/h.

Bruce Rudneski, who works at White Owl Service in Melita, said it was a storm like he's never seen.

The hail poured down and the leaves on trees were shredded.

When the winds suddenly shifted direction, Rudneski knew that was a bad sign and headed for the basement.

“We stayed down there for about 10 minutes until the storm quit," he said.

"[There was] really strong winds, for quite some time, and quite a bit of hail. It was about the size of a thumbnail, not real big hail, but it lasted quite some time, longer than I've ever seen hail last."

With files from CBC News