The probe into Switzerland's second-largest bank by assets relates to a CD with client data bought by the German state of North Rhine-Westphalia.
We already have restrictions on travel in place and now these are being applied very strictly in the case of Germany, a Credit Suisse spokesman told Reuters on Sunday.
As far as I know we have had no contact with the German authorities and cannot comment further, he said.
Credit Suisse, which operates globally in investment banking and wealth management, gained market share at home in the crisis as larger domestic competitor UBS
In 2008, Germany paid for stolen data from Liechtenstein's top bank LGT. Former Deutsche Post chief Klaus Zumwinkel's Liechtenstein trust was uncovered in that data and he admitted to tax evasion in a spectacular case.
Germany's willingness to buy stolen bank data once again has increased the pressure on Switzerland's large private banking industry and stirred emotions in both countries. Germans hold an estimated 200 billion euros in undeclared funds in Switzerland.
Former German finance Hans Eichel called for Credit Suisse's German banking license to be revoked if its bankers were found to have helped German clients evade taxes, Swiss paper SonntagsBlick reported.
If a company does not respect the laws of the land, it cannot operate here , Eichel said in an interview.
The United States already made this clear in the case of UBS. Germany has not acted as tough as this so far, but in view of the scale of the problem, this is what Germany will have to do, he said.
German clients of other Swiss banks have nothing to fear from the probe. None of their accounts were included on the CD obtained by Germany, Swiss paper Sonntag reported German state prosecutor Nils Bussee as saying.
According to the current state of knowledge, no other banks are involved, Bussee said.
(Reporting by Jason Rhodes; Editing by Hans Peters)