A creek in northwest North Dakota was blocked off to prevent runoff from an oil spill from a subsidiary of Occidental Petroleum, the health department said.

The North Dakota Department of Health said about 60 barrels of brine and five barrels of oil were spilled into a small creek in Burke County.

"Impacted water has been diked to prevent further runoff downstream," the health department said in a statement Sunday.

There was no statement from OXY USA Inc. on the release and no cause for the incident was given. There were no statements on the potential impact to public health.

The release is the second reported in North Dakota this month. About 40 barrels, or 1,680 gallons, of brine, a liquid associated with production in the state, spilled into a creek about seven miles west of Williston.

Energy companies inject brine, or salt water, to improve oil and gas production from shale deposits. The Environmental Protection Agency said brine may contain toxic metals and radioactive substances that may be damaging to the environment and public health if released on the surface.

North Dakota lies at the heart of the shale boom in the United States. The North Dakota Industrial Commission in its latest monthly report said oil production in January, the last full month for which data are available, was 1.19 million barrels per day, down 2.5 percent from the all-time high reported in December.