Updated

German stock exchange operator Deutsche Boerse says it and CEO Carsten Kengeter are cooperating with prosecutors investigating purchases by Kengeter of the company's own shares.

Frankfurt-based Deutsche Boerse said in a statement Wednesday that the share purchase took place Dec. 14, 2015 as part of the company's executive pay program.

Deutsche Boerse's disclosure of directors' dealings on its website shows Kengeter bought 60,000 shares on that date for 4.5 million euros ($4.8 million) and he had discussed the purchase publicly.

Deutsche Boerse shares rose after it agreed to what it calls a merger of equals with the London Stock Exchange Group. An agreement on an all-share tie-up is still undergoing regulatory review by the European Commission.