The Swiss stock exchange (SWX) has launched a preliminary investigation into the reporting behaviour of the Credit Suisse Group.
This follows allegations that the group leaked information to financial analysts about its third quarter figures before their release on Thursday.
"We have started an initial investigation to see what really happened," the Swiss Exchange spokesman Leo Hug said on Friday.
"We will go to them and see if there is reason to start a real investigation," he added.
Hints to analysts?
The stock exchange move comes after the "NZZ am Sonntag" newspaper reported that analysts had received hints that CS would announce a third quarter loss of about SFR2 billion ($1.37 billion), including a SFr350 million tax charge.
CS actually reported a loss of SFr2.1 billion which included a group tax charge of SFr410 million.
"We haven't received an enquiry from the SWX but we will certainly cooperate fully if we receive one," CS spokesman Andreas Hildenbrand told swissinfo.
CS has rejected the claims, saying that exchange regulations permitted it to inform analysts if they came to wrong conclusions or assumptions in their reports, provided that such corrections were based on publicly available information.
The penalties for a breach of the bourse rules include a fine of up to SFr200,000 a suspension of trading or delisting. But Reuters news agency notes that the SWX has seldom taken action beyond a reprimand in such cases.
swissinfo with agencies