Washington (CNN) EPA Administrator Scott Pruitt is facing renewed questions about the size and cost of his 24-hour security detail, adding to a string of ethically questionable arrangements or actions on his part that have surfaced over the past year.

Pruitt's security team currently consists of 19 agents and includes a fleet of at least 19 vehicles, a source with direct knowledge of Pruitt's security detail said. With the cost of maintenance, gas, and training for agents, that leaves the dollar amount for his round-the-clock security in the millions.

The size of Pruitt's security is unprecedented. No previous EPA chief has ever received a 24/7 security detail, the agency's inspector general has said. Former EPA Administrator Christine Todd Whitman, who served under George W. Bush, has told CNN she walked to work alone even after the September 11 terrorist attacks, and although she traveled with security, it was never this large.

At the time, members of Congress called Pruitt's beefed up security measures into question, voicing concerns about a "potential waste or abuse of taxpayer dollars."

That increase in spending came as the Trump administration shared plans for cutting the EPA's budget by about 30%, including major cuts to the agency's enforcement work and staffing and the elimination of some programs.

Pruitt's 24-hour security has extended to at least some of his personal trips, according to a letter Democratic Sen. Sheldon Whitehouse sent to the department's inspector general, CNN reported this week . The letter, which was based on information that the Rhode Island senator says he confidentially obtained from an unnamed source, alleges that Pruitt has used his security detail while on unofficial business, including trips home to Tulsa, Oklahoma, a family vacation to Disneyland and the Rose Bowl game.

Pruitt has been under increased scrutiny for citing security as the reason he has flown first class on the government's tab, racking up nearly $200,000 in travel costs. On one trip to Italy, from June 5-12 of last year, his security detail alone amounted to more than $30,000. He has also been criticized for taking private and military flights instead of flying commercial.

In response to the questions about Pruitt's security spending, the EPA has maintained that his security detail was increased because the administrator and his family have faced numerous death threats.

"According to EPA's assistant inspector general, Scott Pruitt has faced an unprecedented amount of death threats against him and his family," the agency said in a statement. "Americans should all agree that members of the President's Cabinet should be kept safe from these violent threats."

An Associated Press report Saturday on Pruitt's security and travel spending heightened scrutiny over the size of Pruitt's security detail.

Pruitt has been at the center of several stories calling into question his ethics and spending practices at the EPA over the past year.

Earlier this week, reports revealed multiple EPA officials who tried to push back or raise alarms about some of Pruitt's spending were sidelined or demoted.

Additionally, Pruitt has faced criticism over an expanding controversy involving a housing arrangement in which he rented a room in Washington, DC, for below market price from a lobbyist and her husband, whose firm lobbied the EPA on behalf of an Oklahoma energy company, ABC News and Bloomberg have reported. The news about the arrangement left senior White House aides exasperated, CNN reported this week

On Friday, CNN reported that the couple, Vicki and Steven Hart, forced Pruitt out of the apartment by changing the code on their locks after the they became increasingly frustrated with him as a tenant.

House Oversight Chairman Trey Gowdy is probing the actions of the embattled EPA administrator, his spokesperson, Amanda Gonzalez, confirmed to CNN on Friday.

But the White House has remained adamant in its support of Pruitt as head of the EPA.

White House press secretary Sarah Sanders told reporters Friday that Trump believes Pruitt has "restored it back to its original purpose of protecting the environment. It's got unnecessary regulations out of the way."