(Corrects first bullet point and paragraph two to say executives sold shares, removing specific reference to individuals, since the company did not disclose all the names; updates share price fall)
* Chairman, other executives traded prior to profit warning * Company says did not issue timely blackout period
* Leadership crisis comes on top of recent product setback * Shares down more than 12 percent
(Adds prosecution comment, updates shares)
By Martin de Sa'Pinto
ZURICH, March 30 (Reuters) - The three top managers at Swiss group Sonova Holding AG, the world's biggest hearing aid maker, have quit after a probe into executive share sales ahead of a recent profit warning.
Chairman Andy Rihs, Chief Executive Valentin Chapero and Chief Financial Officer Oliver Walker are all stepping down after executives sold shares or options earlier this month, Sonova said on Wednesday, sending its shares down 12 percent.
The statement sparked concerns a leadership crisis may hit the company's business and add to a recent product setback.
Swiss exchange SIX has opened a preliminary investigation with which the company said it would co-operate. Swiss prosecutors said they were considering whether to open criminal proceedings, a spokeswoman said.
SIX data showed insiders sold equities and warrants for some 45 million francs ($49 million) in the period immediately prior to the profit warning, more than 20 times the value of such trades throughout February.
On March 16, Sonova lowered its profitability and sales outlook for the year after being hit by a product recall, slowing sales and the strong franc.
"The leadership change comes when a big product launch is under-delivering and when two acquired businesses struggle," Kepler Capital Markets analyst Florian Gaiser said in a note.
"Given the discontinuity, the significant drain in know-how and the importance of leadership for customer relationships in the hearing aids business, we believe the change comes at a very bad moment for the company's business," Gaiser said.
The departures come after a string of high-profile insider dealing cases in major financial centres following the financial crisis.
Hedge fund boss Raj Rajaratnam is on trial in Wall Street's biggest trading scandal in decades, while last year the UK fined the chief executive, chief commmercial officer and exploration manager of Turkish oil expansion firm Genel Enerji for dealing in Heritage Oil on the basis of insider information.
UNTIMELY TRADING
Sonova has clinched the global top spot in the lucrative market for hearing aids in recent years, competing with Germany's Siemens AG and Danish companies GN Store Nord A/S and William Demant Holding A/S.
Sonova said it had failed to issue a timely internal blackout period for trading in its shares and options prior to the warning.
"As a result of this failure, there were trades that should not have taken place during that period," it said following an investigation by a law firm commissioned by the company.
Spokesman Sacha Wigdorovits said executives had cashed in options in the period but declined to say who had sold.
The company said while Rihs had sold shares, the investigation had not found he was aware of the impending profit warning at the time. Chapero and Walker both tendered their resignations, while Rihs will step down as chairman but remain a director.
Sonova shares -- down 12 percent at 82.05 francs by 1525 GMT -- hit a 2011 high of 128 francs on March 7, a day before Rihs sold 300,000 shares, but had fallen back to 115.40 francs on March 15, the day before the warning.
Rihs still owns around 9 percent of the company, Thomson Reuters data showed. The Rihs family group holds around a quarter of Sonova's shares, the group's spokesman said.
Sonova management board member Alexander Zschokke will take over as acting CEO. Robert Spoerry, a former CEO of precision-measuring device maker Mettler Toledo, has been appointed chairman. (Additional reporting by Alex Smith in London; Editing by Dan Lalor and David Holmes) ($1 = 0.9214 Swiss franc)