The leak from the 8-inch underground pipeline was detected Wednesday when workers from Phillips 66 Co., based in Houston, found the pressure on the line had dropped, NBC News reported.
A U.S. Department of Transportation spokesman said the leak, which occurred about 15 miles from Lodge Grass, Mont., was under investigation but posed no safety threat to the public and did not immediately affect any waterways.
The Crow Tribe and U.S. Environmental Protection Administration officials also were investigating.
The same pipeline broke twice in one week in 1997, spilling an estimated 2,300 barrels of gasoline near Lodge Grass and Banner, NBC News said.
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