The Internet lottery company issued a profit warning based on a reported jackpot on Sunday only to withdraw the warning on Monday, saying the reported jackpot win had been mistaken.
"We are taking a look to see if market manipulation may have been involved," a Bafin spokeswoman said.
A Tipp24 spokesman said the Bafin probe was routine and the company was not concerned by the development.
(Reporting by Jonathan Gould and Anneli Palmen; Editing by Christoph Steitz)