An employee on a pump station heard what was described as a mechanical bang early Tuesday morning, an official told CBS News.

The cause of the rupture and the total volume of oil released after the North Dakota spill remain unclear, officials said.

The Keystone Pipeline in North Dakota was shut down Tuesday after reports of a "bang" and spilled oil, according to officials ...

The nearly 2,700-mile Keystone oil pipeline was shut down Tuesday morning after it ruptured in North Dakota, halting the flow ...

A portion of the Keystone Pipeline ruptured near Fort Ransom, North Dakota, around 7:44 a.m., according to local reports.