WATFORD CITY - Crews were working Friday to regain control of an oil well south of Watford City after a blowout prompted 15 workers to flee for safety.

The oil well blowout occurred Thursday after a piece of equipment failed at a well about seven miles north of the Theodore Roosevelt National Park North Unit, said Department of Mineral Resources Director Lynn Helms.

No injuries were reported. The initial release sprayed a mist of oil and water on to snow that is on top of the ice-covered Cherry Creek, Helms said.

“To the best of our knowledge, nothing has gotten into the water,” Helms said.

The company that operates the site, Whiting Oil and Gas, estimates about 50 barrels of flowback water were released but contained on site within a berm, said spokesman Jack Ekstrom. Hydraulic fracturing had been completed on the well and the fluid that was released was the water-based solution that flows back to the surface.

A leak in the seal of the blowout preventer caused the incident, Ekstrom said.

The well continued releasing fluids Friday at a rate of about 200 barrels per hour, but it was being directed to tanks and contained on site, Ekstrom said.

Crews from Wild Well Control were brought in to assist, and Whiting officials expected to resume normal operations late Friday or Saturday, Ekstrom said.

The 15 workers who ran away from the well left their pickups at the site, said McKenzie County Emergency Manager Jerry Samuelson.

The workers called the McKenzie County Sheriff’s Office and Samuelson said he directed a school bus that was in the area to pick up the workers.

“When that thing blows, you just never know,” Samuelson said. “There’s a possibility of explosion.”

Several state agencies, including inspectors from the Department of Mineral Resources and the North Dakota Department of Health, responded to the scene.

Kris Roberts, with the health department’s Division of Water Quality, said the total amount spilled was not yet known. Most of the release was being contained within the berm that surrounds the well, but some spray was coming off Friday that was mostly natural gas and water vapor, Roberts said.

An inspector had to wait until the spray stopped to determine how large of an area it affected, Roberts said.

“It’s still a tad dangerous up there,” Roberts said mid-day Friday.

Helms said the cause of this incident will be closely examined because blowouts carry serious health and safety risks.

In 2012, a worker died when he was hit by pickup during the chaos after a blowout in Williams County.

But in Thursday’s incident, most of the release was contained on site and crews followed emergency procedures, Samuelson said.

“The best-case scenario happened,” Samuelson said.

Bob Wisness, who lives about a mile away from the well, said he saw emergency vehicles and what looked like a green vapor after the incident. He said he received a message from Whiting that a blowout occurred. Wisness said he didn’t feel he was in danger, but he started texting friends who live near the site but were out of town.

“There are well sites that are closer to people’s homes. I’m glad it’s not me. Other people have good reason to worry about it,” Wisness said.

Kathleen J. Bryan contributed to this report.