Shares of Super Micro Computer tumbled more than 20% in premarket trading on Wednesday as an unclear timeline for its annual report along with weak quarterly forecasts fanned investor worries about the AI-server maker.

Super Micro says its special committee has so far found that its audit committee “acted independently and that there is no evidence of fraud or misconduct on the part of management” or the board.

Super Micro Computer, whose auditor unexpectedly stepped down last week, flagged uncertainty on Tuesday about the timing of its annual report but said a probe about accounting practices had not found evidence of fraud by the company.