Six House Democrats asked the Justice Department and FBI Friday to open a criminal investigation into embattled Environmental Protection Agency Administrator Scott Pruitt "for using taxpayer-funded resources for the personal gain of himself and his family.”

“At the very least, we know that federal ethics laws bar public officials from using their position or staff for private gain,” the Democrats, led by Rep. Don Beyer of Virginia, wrote in a letter to FBI Director Christopher Wray and Acting Assistant Attorney General John Cronan.

“Administrator Pruitt has certainly done just that. Further, his actions related to his wife’s employment and the quid-pro-quo condo situation with industry lobbyists may have crossed a line into criminal conduct punishable by fines or even time in prison.”

Other Democrats signing the letter include Reps. Gerald Connolly of Virginia, Jamie Raskin of Maryland, Ruben Gallego of Arizona, Ted Lieu of California, and Pramila Jayapal of Washington.

The letter marks the first request from Congress for a criminal probe of Pruitt.

The EPA chief is already facing a dozen federal investigations, but they are mostly being conducted by the EPA’s inspector general, congressional committees, and the White House, and focus on whether he has violated federal ethics rules.

The roster of issues under investigation include Pruitt’s $50-per-night condo rental deal with the wife of an energy lobbyist who had business before the EPA, his spending of more than $3.5 million on security, his $43,000 secure phone booth , frequent first-class travel , and allegations that he retaliated against employees who questioned his judgment.

Serious new allegations have surfaced this week, involving Pruitt’s use of public office for personal reasons.

Internal emails show that Pruitt assigned an EPA scheduler to arrange a meeting with the president of the fast-food company Chick-fil-A to discuss his wife becoming a franchise owner. Pruitt this week said he and his wife were “very excited” about the prospect of becoming owners.

The move could potentially violate the Hatch Act, which prohibits Cabinet-level officials from using federal staff for duties other than running the agency.

Also this week, congressional testimony became public showing an EPA aide, during official work time, tried to obtain a mattress for Pruitt from the Trump International Hotel. And Pruitt used his round-the-clock security detail to pick up dry cleaning and body lotion, according to another report.

Federal rules say public officials cannot receive gifts from subordinates, including unpaid services. The rules also prevent them from using their office for private gain.

[Related: Top Pruitt aide resigns after Trump Hotel mattress story]