Officials estimate more than 176,000 gallons of crude oil leaked from a pipeline into a North Dakota creek.
State environmental scientist Bill Suess (sees) says a landowner discovered the spill on Dec. 5 near Belfield.
Suess says the oil has migrated more than 5 miles from the spill site along Ash Coulee Creek. The creek feeds into the Little Missouri River, but Suess said the oil didn't make it there. He says the spill appears to be contained and no drinking water sources were affected.
Suess says about 37,000 gallons of oil has been recovered.
Wyoming-based Belle Fourche (foosh) Pipeline operates the pipeline. Spokeswoman Wendy Owen says it was equipped with monitoring equipment that failed to detect the leak.
The cause of the rupture is under investigation.