BILLINGS, Mont. (AP) — Environmental groups are calling for a moratorium on coal leasing in the Powder River Basin of Montana and Wyoming until the federal government reviews the program.

Representatives of 21 groups including Greenpeace and the Sierra Club requested the moratorium Monday in a letter to newly-confirmed Interior Secretary Sally Jewell.

The Powder River Basin produces more coal than any other area of the country.

As companies seek to ramp up coal exports, the environmentalists say the government needs to make sure companies are paying proper royalties. They also want more attention given to the climate change impacts of greenhouse gasses emitted when coal is burned.

The Interior Department's Inspector General and the Government Accountability Office have been investigating alleged problems within the coal leasing program at the request of Congress.

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