Kraig Naasz, president and CEO of the National Mining Association, is stepping down after three years of heading the trade association.

While reason for Naasz’s departure is not clear, the NMA board decided Monday to relieve him of his position.

NMA spokesman Luke Popovich confirmed the board’s decision but would not detail Naasz’s situation.

“Mr. Naasz has taken an extended leave of absence,” Popovich said. He declined to elaborate on the change in leadership.

The decision comes as the mining industry is expected to face increased challenges next Congress. Naasz’s role had been under scrutiny for at least six months, according to one industry lobbyist, who said the association had called on external sources to review his performance.

The move was first reported by the Hill.

In the interim, Harold Quinn, NMA chief legal counsel and senior vice president, will head the organization.

This is the second time Quinn has taken on the role. He served as interim CEO after Jack Gerard left the mining association in 2005 for the American Chemistry Council.

“He’s well-suited to run the operation,” Popovich said.