U.S. Sens. John McCain and Jeff Flake can’t understand why federal authorities have refused Arizona Gov. Jan Brewer’s offer to use state money to keep the Grand Canyon open during the government shutdown.

Several businesses have made similar pledges, but they’ve been rejected by the National Park Service.

A park official says as long as the federal government remains shut down, such a plan isn’t an option.

The shutdown that began Tuesday has led to furloughs for about 2,200 people who work at Grand Canyon National Park and its hotels.

McCain and Flake sent a letter Friday to Department of the Interior Secretary Sally Jewell.

The two Arizona Republicans say “federal statutes extend broad discretionary authority” for Sewell to accept donated funds for purposes of operating the national park system.

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Photo Credit: The Colorado River flows through the Grand Canyon on the Hualapai Indian Reservation near Peach Springs. Joshua Lott / Reuters