Two top Environmental Protection Agency officials have resigned, amid continued questions over multiple controversies with EPA head Scott Pruitt in charge, CBS News' Jacqueline Alemany has confirmed.

Albert "Kell" Kelly has resigned as a senior adviser at the EPA running Pruitt's Superfund task force, as has Nino Perrotta, head of Pruitt's highly scrutinized, around-the-clock security detail. Perrotta had planned to retire this summer.

Kelly's departure comes after Pruitt was asked repeatedly about the senior adviser during a full day of congressional hearings last week. Also last week, Democrats asked the EPA's internal watchdog to review Kelly's "ethical, regulatory and potential legal issues." Kelly, an old business associate of Pruitt's, had recently been barred from working in finance because of a banking violation, although the nature of the violation is unclear.

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Pruitt's security detail run by Perrotta has come into question, with the Associated Press reporting Pruitt has a 20-member full-time security detail that has cost millions since he took office. Pruitt is set to be interviewed by the House Oversight and Government Reform Committee staff Wednesday.

Pruitt praised both Kelly and Perrotta in statements.

"Nino Perrotta has selflessly served the American people for more than 23 years, beginning his career as a special agent with the United States Secret Service and then serving four EPA administrators," Pruitt said. "His hard work and dedication will be missed by all those who worked with him. I want to thank him for his service and wish him the very best in retirement."

Pruitt had even lengthier praise for Kelly.

"Kell Kelly's service at EPA will be sorely missed. In just over a year he has made a tremendous impact on EPA's Superfund program, serving as chair of the Superfund Task Force and presiding over the development of the steps necessary to implement the recommendations in the report," Pruitt said in a statement. "Kell has made a point to visit dozens of Superfund sites across the country and has met directly with impacted citizens, community groups and responsible parties. Kell has served in a way that puts the needs of the American people and communities first, while respecting the work committed to by responsible parties."

In a statement, former Oklahoma governor and former CEO of the American Bankers Association called Kelly a "man of high integrity."

Pruitt's rental agreement for a condo connected to a Washington lobbyist, the hefty raises two top aides of his received, his security expenses and other controversies have continued to dog Pruitt, who has lasted more than some embattled Cabinet members and nominees. Last week, the president's pick to run the Department of Veterans Affairs, Ronny Jackson, withdrew his name less than 72 hours after a slew of unsubstantiated allegations about his conduct as the president's physician emerged. Now, Jackson will no longer be the president's physician either.