Story highlights Sen. Maria Cantwell of Washington state made the request

Zinke's use of Interior and other helicopters was revealed earlier this year

Washington (CNN) A Democratic senator is calling for the investigation into Interior Secretary Ryan Zinke's travel to include his use of government helicopters.

Zinke's use of Interior Department and other helicopters was revealed earlier this year when the department released his office and travel schedules in response to Freedom of Information Act requests. Documents show that helicopter trips to and from events within a few hours of his Washington office cost taxpayers more than $14,000.

Politico first reported on the flights.

Sen. Maria Cantwell, a Democrat from Washington state, called for the investigation to include Zinke's "taxpayer-funded helicopter rides."

"If he misused public funds, he should write the Treasury a check for the full amount & apologize," she said.

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