The Energy Department says Energy Secretary Rick Perry has taken at least six trips on government or private planes costing an estimated $56,000.
The report comes as top officials in the Trump administration undergo scrutiny for their use of costly private or military air travel at taxpayers' expense.
Three of Perry's trips were on government planes, including one on an Energy Department plane to the Hanford nuclear site in Washington state, and two military flights to national labs in Idaho and New Mexico.
Perry also flew on private planes to visit a Pennsylvania coal plant and nuclear sites in Ohio and Kansas City.
Perry's office released details about the flights to the House Oversight Committee, which is investigating non-commercial travel by the Trump administration.
The inspector general at the Environmental Protection Agency says it is expanding an inquiry into Administrator Scott Pruitt's frequent taxpayer-funded travel.
The watchdog office said the review will now include all travel by Pruitt through Sept. 30. Previously, the inspector general was focusing on Pruitt's travel to his home state of Oklahoma through July 31.
A spokeswoman said Friday the scope of the review was expanded after requests by members of Congress,
The Associated Press and others reported in July that Pruitt traveled to Oklahoma at least 10 times.
An EPA spokeswoman said the trips were warranted.
The inspector general's office said its review will look at whether Pruitt followed EPA travel policies and whether those policies are sufficient to prevent fraud, waste and abuse.
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