The State Health Department is investigating what they are calling a 'significant release from a pipeline.'

The department says they aren't sure how much oil leaked into the Ash Coulee Creek 16 miles northwest of Belfield but that the line has been shut off and is not leaking further.

They say they are working to boom the creek about two and a half miles downstream. As of now, the Little Missouri River is not believed to be in immediate danger.

The cause of the leak is yet to be determined, but crews are expected to work through the night.