TIOGA, N.D. — A mechanical failure caused oilfield wastewater to spill and contaminate an agricultural field in Williams County on Saturday, April 20, the North Dakota Department of Health said.

Initial estimates show the spill involved about 390 barrels, or 16,380 gallons, of produced water, which is a waste byproduct of oil production, the Bismarck Tribune reported.

The mechanical failure occurred at a saltwater disposal facility about 8 miles south of Tioga that is owned and operated by Hess Bakken Investments II, health officials said.

Health department personnel are inspecting the site and will monitor the investigation and cleanup.