The North Dakota Oil and Gas Division reported Tuesday an oil spill that occurred last month in Burke County is now estimated to be larger than initially reported.
About 400 barrels, or 16,800 gallons, of oil spilled on Feb. 21 at a well about 4 miles north of Flaxton, or 2½ miles south of the Canadian border, according to an incident report filed Tuesday.
The spill was caused by a broken valve on a storage tank and contained to the well site.
Cornerstone Natural Resources is listed as the operator of the well, but the company is transitioning ownership to Challenger Point Energy. Challenger Point Energy will be responsible for cleanup, regulators said.
Cornerstone Natural Resources initially reported the spill as less than 100 barrels, or 4,200 gallons.
An inspection of the site shows that the spill and most of the impacted soil have been removed, regulators said. Cleanup will continue this spring.