Former executives at Tether-backed German tech company Northern Data have sued the company, accusing it of wrongful termination, after they raised concerns about the company's financial health and accused it of tax evasion.

Northern Data, Europe's largest Bitcoin miner, also operates data centers for artificial intelligence.

Joshua Porter and Gulsen Kama allege that Northern Data misled investors about its financial condition, concealed the fact that it was "pre-bankrupt" and evaded paying tens of millions of dollars in taxes.

The allegations come amid rumors that Northern Data is considering an initial public offering (IPO) of its artificial intelligence unit in the US, which could be valued at up to $16 billion, according to Bloomberg.