On the same day Health and Human Services Secretary Tom Price resigned after a scandal over his use of taxpayer-funded private flights, Interior Secretary Ryan Zinke also came under investigation for his use of private planes, according to Politico.

Federal investigators are now looking into Zinke’s travel expenses during his tenure after Politico reported last week that he had chartered a $12,000 flight from Las Vegas to an airport near his hometown in Montana and another flight between two Caribbean islands, according to the Washington Post. The Interior Department’s inspector general office launched its investigation into whether those flights and other travel expenses could be considered legitimate expenses on Friday.

Zinke’s flight from Las Vegas invited scrutiny and criticism because he was prevented from taking a commercial flight by a dinner event associated with a major campaign donor. At the event, Zinke gave a speech to the Vegas Golden Knights, a hockey team owned by a major donor to his former congressional campaigns.

Zinke, in the aftermath of the revelations last week, called the controversy over his expenses “a little B.S” and insisted he submitted his travel plans to oversight and followed the law.

Arizona Rep. Raul Grijalva, a senior Democrat on the House Natural Resources Committee, and Virginia Rep. Donald McEachin, a member of an oversight subcommittee on investigations, requested the investigation. Grijalva and McEachin wrote in a letter to the inspector general that billing those flights as government expenses might violate rules because the trips involved “events that may not be taxpayer reimbursable,” according to the Los Angeles Times.

Grijalva and McEachin also encouraged investigators to look at all Zinke’s travel expenses, as well as any taxpayer-funded travel for his wife, who chairs a GOP Senate campaign. A spokesperson for the inspector’s office confirmed the investigation would probe all taxpayer-funded travel expenses.

Price resigned Friday after it was revealed he had racked up more than $1 million in taxpayer-funded travel expenses since May. EPA Administrator Scott Pruitt also has been facing questions over his travel expenditures.