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Bitmain Technologies Ltd.’s billionaire founder Wu Jihan announced Tuesday the resignation of his co-founder, a surprise ouster that appeared to resolve a struggle for control of the world’s largest crypto-mining startup.

Micree Zhan Ketuan, who started Bitmain with Wu six years ago, no longer holds any position at the Beijing-based company effective immediately, Wu said in an internal memo obtained by Bloomberg News. The crypto-entrepreneur warned employees against taking further instructions from Zhan or attending any meetings he convenes, threatening staff with dismissal or criminal charges. Nishant Sharma, a company spokesman, declined to comment on the memo.

“If employees cause any harm to the company’s economic interests, the company will investigate their civil or criminal liability in accordance with the law,” Wu wrote in the memo, signing off as Bitmain’s co-founder and chairman. Zhan didn’t immediately reply to an emailed query and calls to his personal phone went unanswered.

Bitmain’s two co-founders had long served as co-CEOs but were replaced this year by Wang Haichao, at a time the company was grappling with lay-offs and a cash crunch triggered by Bitcoin’s price plunge. Tuesday’s surprise memo is sure to stoke more questions around the world’s largest producer of crypto mining rigs, which Bloomberg News reported had previously failed to pursue a Hong Kong listing of as much as $3 billion.

Bitmain, which was valued at about $15 billion in a private funding round last year, continues to grapple with an uncertain home regulatory environment even as its fortunes wax and wane along with the price of Bitcoin. It’s also said to have considered a U.S. debut, long before rival Canaan Inc. filed for its own U.S. initial public offering.

Wu and Zhan hold 21% and 37% of the company, respectively, according to Bitmain’s IPO prospectus for Hong Kong. Wu was Bitmain’s business head, an avid supporter of digital tokens like Bitcoin Cash. Zhan, on the other hand, led the company’s chip designing team and its foray into artificial intelligence chip-making. This year, Wu founded a crypto financial services startup called Matrixport. He recently took over Zhan as the legal representative of Bitmain’s Beijing entity, according to public company registration information.