The White House said Wednesday that the government is investigating a protest in which anti-fossil fuel activists, branded “eco-terrorists” by an oil group, broke into several pipeline facilities.

On Tuesday, protesters cut through fences and manually closed pipeline valves in North Dakota, Montana and Minnesota. The pipelines in those states provide about 2.5 million barrels of oil per day to refineries in the U.S., according to the American Fuel and Petrochemicals Manufacturers.