Bitmain Technologies’ billionaire founder Wu Jihan announced on Tuesday the resignation of his co-founder, a surprise ousting that appeared to resolve a struggle for control of the world’s largest cryptocurrency mining start-up. 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 cryptocurrency 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 did not immediately reply to an emailed query and calls to his personal phone went unanswered. Bitmain’s two co-founders had long served as co-chief executives, 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 maker of cryptocurrency mining rigs, which Bloomberg News reported had previously failed to pursue a Hong Kong listing of as much as US$3 billion. Bitmain, which was valued at about US$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 is also said to have considered a US debut, long before rival Canaan Creative filed for its own American initial public offering . Wu and Zhan hold 21 per cent and 37 per cent 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 in designing artificial intelligence chips. This year, Wu founded a cryptocurrency financial services start-up called Matrixport. He recently took over Zhan as the legal representative of Bitmain’s Beijing entity, according to public company registration information. For more insights into China tech, sign up for our tech newsletters , subscribe to our Inside China Tech podcast , and download the comprehensive 2019 China Internet Report . Also roam China Tech City , an award-winning interactive digital map at our sister site Abacus .