BILLINGS, Mont. (AP) -- Lawmakers are asking the U.S. Department of Interior to review whether companies are shortchanging federal and state governments out of millions of dollars in royalties on coal exported to foreign markets.

Friday's request from Oregon Sen. Ron Wyden and Alaska Sen. Lisa Murkowski comes as U.S. coal exports hit a record of an estimated 124 million tons last year. That includes coal shipped to Asia from the Powder River Basin of Montana and Wyoming.

The senators want Interior Secretary Ken Salazar to determine whether companies have violated federal leasing law by paying royalties on the coal's mine price, then selling it overseas at a higher price through affiliated brokers.

National Mining Association spokeswoman Carol Raulston says companies believe they are complying with the law.

The concerns over export royalties were first reported by Reuters.

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