According to the Bismarck Tribune, an Occupational Safety and Health Administration official said the services company was Legendary Field Services of Watford City.

"Office supervisor Eric Brooks said it appears from preliminary reports that the men were removing a tube on the well heater component when fluids somehow ignited," the newspaper reported.

"Both men were burned and the owner's injuries were fatal, he said."

The accident is the first US oil-field fatality reported this year according to Associated Press.

An investigation is underway and names of the victims have not yet been released.