Most of the waste from a pipeline release in North Dakota has been recovered, though the spill impacted a wetland area, the Health Department said.

The North Dakota Department of Health said it was notified of a pipeline leak in Burke County, in the northwest of the state along the U.S.-Canadian border.

"The report indicates that the pipeline, owned by Oasis Petroleum LLC, leaked approximately 500 barrels of produced water [brine], of which 475 barrels have been recovered," the department said Wednesday in a statement. "The spill has impacted a nearby wetland."

The incident is at least the fifth such release of its kind this year in the state at the heart of the shale oil boom in the United States. About 100 barrels of brine were released in two separate incidents last month.

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

The State Health Department said it and oil spill responders were on site observing the cleanup operation. There was no statement on the incident from Oasis Petroleum and no information on the status of the pipeline.

North Dakota oil production is slowing down in part because energy companies are spending less in the era of low oil prices. The state, the No. 2 oil producer in the country after Texas, produced 1.2 million barrels of oil per day in January, a 3 percent decline from the all-time record set in December.