BISMARCK — An estimated 35,700 gallons of produced water spilled over a week ago at an oil well pad in McKenzie County, N.D., according to a press release from the state Department of Environmental Quality.

Produced water, or brine, is a mixture of saltwater, oil and sometimes, drilling fluids, that is created as a byproduct of oil and gas production.

The spill, which occurred about 10 miles northeast of Keene, impacted nearby farmland. The incident was caused by a leak in a small pipeline to the produced water storage tank.

Newfield Production Co., which was responsible for the spill, estimated that only 1,260 barrels of brine had spilled when it reported the incident to the state. Later investigation found the company had significantly underestimated the magnitude of the spill. It's unclear if the company accidentally reported incorrect information or purposefully misled the department. A representative of the department did not respond in time for publication of this article.

The department said officials will continue inspecting the site and monitoring remediation efforts.