A group of investors has filed a class-action complaint against Gemini Trust Co. and its founders, Tyler and Cameron Winklevoss, alleging that the U.S. cryptocurrency exchange sold unregistered securities in the form of interest-bearing accounts.

In mid-November, the Winklevoss twins halted redemptions after Gemini’s business partner Genesis Global ran into financial issues due to FTX’s sudden collapse. According to reports, Genesis had $175 million locked in FTX before the exchange filed for bankruptcy.

Picha and Hastings allege that Gemini then refused to honor any further investor redemptions, leading to the loss of all holdings in the program.