With the latest announcement, he is conducting about a half-dozen investigative audits of Pruitt's travel, security and other matters.
During hearings last month, Pruitt, who was confirmed February 17, 2017, justified his security spending by citing threats he had received since taking office.
Chuck Grassley warned Tuesday he may call on Environmental Protection Agency Administrator Scott Pruitt to resign if his agency does not take a fairer approach to issuing waivers to the large refineries that allow them to skirt biofuels regulations. Pruitt is also under fire for substantial raises afforded to two young staffers he brought with him from Oklahoma, where he previously served as a Republican state attorney general.
This time, EPA Administrator Scott Pruitt will testify earlier than a Senate Appropriations subcommittee that oversees the company's finances.
EPA's inspector general revealed earlier this week that Pruitt requested and received 24-hour security beginning his first day in office.
Most of the committee's six Democratic members have been vocal oponents of Pruitt's regulatory rollbacks at EPA and have criticized him for alleged ethical missteps while in office related to his spending and his lease of a room in a Washington condo linked to an energy lobbyist.
Despite the mounting investigations, President Donald Trump has said he supports Pruitt.
The EPA has said that the first-class flights were necessary, because of security threats against Pruitt.
Several Democrats on the subcommittee, including Senator Diane Feinstein and Senator Patrick Leahy, have called for Pruitt's resignation. Asked Friday if he still had confidence in Pruitt, Trump told reporters, "I do". "Forget about your own ego and your first class travel and your special phone booths that just make you a laughingstock and your agency a laughingstock".