The Zurich public prosecutor has opened an inquiry into the controversial sale of shares at hearing aid maker Sonova.
Three top managers resigned after the firm admitted mistakes leading up to a profit warning that was preceded by a huge share sell-off. Chairman Andy Rihs denied accusations of insider trading.
The prosecutor has already questioned various people about the sale and has asked Sonova to provide documents.
The board of directors said it was supporting the inquiry in order for the events to be “fully cleared up”.
The issue is also being investigated by the Swiss stock exchange.
An earlier investigation carried out by a German law firm at the behest of Sonova found no evidence of wrong-doing. The probe blamed a failure by the company to make public its problems early enough and to initiate a share trading ban in time to stop transactions.
swissinfo.ch and agencies