News of the resignation of Molycorp CEO Mark Smith caused the company’s stock price to fall in after-hours trading on Tuesday. Shares of Molycorp (NYSE:MCP), a leading low-cost rare earth company in the US, dropped 8.21 percent, to $10.40, in the hours following the news.

A company statement notes that Constantine Karayannopoulos has been named interim president and CEO, effective immediately. Karanyannopoulos is director and vice chairman of the board and has previous experience as the president and CEO of Neo Material Technologies (TSX:NEM).

The board of directors sees the move as “a natural inflection point, as it transitions its focus from development to ongoing operations, to bring in a proven business leader with industry experience, a track record of operational excellence and management experience to execute Molycorp’s strategy,” according to the company.

The news of Smith’s resignation came on the back of a November statement from the company that indicates it was subject to an investigation by the SEC “pertaining to, among other things, the accuracy of the Company’s public disclosures.” Following the announcement in November, share prices also took a dive to their lowest level since the company’s 2010 IPO, according to Bloomberg.

The chairman of the board, Ross R. Bhappu, said in a statement, “[t]he Board of Directors thanks Mark Smith for his significant contributions and leadership over the past four years that have brought Molycorp to this natural transition into an ongoing operating business, and we wish him well in his future endeavors.”

The company remains confident in Karayannopoulos’ ability to manage the company and its subsidiaries.