Don Blankenship, the embattled chief executive of Massey Energy, resigned Friday in a move that might enable the company to improve relations with federal regulators but might also hasten a takeover.

Blankenship, 60, and Massey, one of the country’s largest coal producers, have been under fire since an explosion in April at a mine in West Virginia in which 29 workers were killed. The explosion, at the Upper Big Branch mine, was the nation’s worst coal mining accident in 40 years.

Since then, the company has been hit by civil and criminal investigations and damage suits, and regulators have stepped up investigations of several company mines for possible infractions.

“After almost three decades at Massey, it is time for me to move on,” Blankenship said in a statement. His resignation will be effective Dec. 31.

He will be succeeded by Baxter Phillips Jr., president of Massey, as chief executive and by retired Adm. Bobby Inman, a former senior Central Intelligence Agency official and the lead independent director on the Massey board, as nonexecutive chairman.

Reports of possible takeover bids have been swirling for more than a month. The leading contender for such a takeover has been Alpha Natural Resources, which has made a bid.