A power struggle at the world's largest crypto mining start-up has resulted in the surprise ouster of one of its co-founders.

Beijing-based Bitmain Technologies has fired co-founder and executive director Micree Zhan Ketuan, according to an internal memo sent to staff on Tuesday, which was seen by «CoinDesk

His role will be taken over by Jihan Wu, who founded the firm with Zhan six years ago, and is now chairman of the board. Wu is Bitmain's head of business, while Zhan led the company's chip designing team. The pair were previously co-CEOs, but were replaced by Wang Haichao earlier this year.

«Bitmain’s co-founder, chairman, legal representative and executive director Jihan Wu has decided to dissolve all roles of Ketuan Zhan, effective immediately,» the memo sent by Wu, headlined «Important Notice» said. Wu also warned staff not to take any instructions from Zhan or take part in meetings with him, threatening dismissal to those who violate the notice.

Failed IPO

Bitmain is a major manufacturer of bitcoin mining equipment, and the company grew along with the crypto-mining boom. The falling price of bitcoin resulted in a cash crunch and layoffs for the company.

The firm was valued at $15 billion in a private funding round in 2018. In September 2018, the firm filed for an IPO in Hong Kong, in an attempt to raise $3 billion, but was unsuccessful.

According to the IPO prospectus, Zhan was a major shareholder of Bitmain’s holding company, owning 36 percent, while Wu owned 20 percent.