BISMARCK, N.D. (AP) — A pipeline that carries tar sands oil from Canada through seven states has leaked an unknown amount of crude oil over more than quarter-mile swath in northeastern North Dakota, state environmental regulators said Wednesday.

State Environmental Quality Chief Dave Glatt told The Associated Press that regulators were notified late Tuesday night of the leak near Edinburg, in Walsh County. Glatt said pipeline owner TC Energy shut down the pipeline after the leak was detected. The cause of the spill is under investigation.

The Calgary, Alberta-based company formerly known as TransCanada did not immediately respond to phone messages seeking comment Wednesday.

State regulators were on the scene Wednesday afternoon, and they estimated that the area of the spill was 1,500 feet long by 15 feet wide. Glatt said some wetlands were affected, but not any sources of drinking water.

The company was still working to contain the spill Wednesday afternoon.

Crude oil began flowing through the $5.2 billion pipeline in 2010. It is part of a system that also is to include the proposed $8 billion Keystone XL pipeline designed to transport the oil from western Canada to terminals on the Gulf Coast.

Earlier Tuesday, the U.S. State Department held the sole public meeting on a new environmental review of the long-stalled proposal. A federal judge blocked it last year, saying more environmental study was needed.

The original Keystone is designed to carry crude oil across Saskatchewan and Manitoba, and through North Dakota, South Dakota, Nebraska, Kansas and Missouri on the way to refineries in Patoka, Illinois, and Cushing, Oklahoma. It has experienced problems with spills in the past, including one in 2011 of more than 14,000 gallons of oil in southeastern North Dakota, near the South Dakota border.

In 2017, the pipeline leaked an estimated 210,000 gallons of oil onto agricultural land in northeastern South Dakota, in a rural area near the North Dakota border.