CHEYENNE, Wyo. (AP) — Federal officials say they misspoke when they recently announced their approval of a major surface coal mine expansion in Montana.

U.S. Interior Department spokeswoman Heather Swift said Thursday that the expansion is under review. She says "internal miscommunication" led to the incorrect announcement last week about Westmoreland Coal Company's Rosebud Mine.

Officials with Englewood, Colo.-based Westmoreland didn't immediately respond to a request for comment Thursday. The company's stock price briefly jumped last week after the inaccurate statement.

Swift says the Interior Department plans to release a draft study of the expansion for public comment. The study is part of a process that typically takes several years and culminates with the coal being offered at auction.

The mine supplies coal for one of the largest power plants in the western U.S. The expansion would keep the mine operating another 19 years.