North Dakota state environmental regulators on Thursday announced that about 383,000 gallons of crude oil had leaked out of the controversial Keystone pipeline. The spill affected about 22,500 square feet of land near Edinburg in Walsh County. According to regulators, it did not affect any sources of drinking water, but did cover an estimated half-acre of wetland. The pipeline has been shut down since crews discovered the leak on Tuesday night, but a clean up of the spilled oil has yet to be announced, according to Karl Rockeman, director of the state Department of Environmental Quality’s division of water quality. “It is one of the larger spills in the state,” Rockeman said in an email on Thursday.

The pipeline has been the subject of environmental protests for years, in large part because it carries crude oil from Canada’s tar sands, known as the dirtiest oil on the planet. The pipeline has had more than a dozen spills since it went into operation in 2010, according to a the National Resources Defense Council. “Tar sands oil is simply not worth the increased risk of pipeline failure and massive global environmental costs,” Anthony Swift, director of NRDC’s Canada Program, said in a statement. “... In this moment of climate crisis, this spill underscores, yet again, the need to move away from dirty fossil fuels and toward clean energy,” Swift said. This latest spill comes as the company lobbies to build the Keystone XL pipeline, that would carry the tar sands’ crude oil across the United States to refineries in Texas.