Bernie Ecclestone has not been seen at Hockenheim so far, raising suggestions he is afraid of arrest.
German newspapers - including FT Deutschland, Suddeutsche Zeitung and Munchner Merkur - say corrupt former F1 banker Gerhard Gribkowsky has this week spent no fewer than eight hours in conversation with Munich prosecutors.
The subject? A possible indictment against F1's chief executive.
Munich prosecutors on Friday declined to comment.
"We do not disclose details at each step of an investigation," said a spokesman.
Ecclestone, however, insists he is not staying away from Germany this weekend for fear of ending the day in custody, also charged with corruption.
"I am going. I will be there on Saturday," the Briton is quoted by the Hamburger Abendblatt.
But is he afraid of arrest?
"I have nothing to do with the case," Ecclestone insisted.
Major F1 sponsors, however, are not so convinced. The Times reports that companies including UPS, Allianz and Petronas "have examined details" of the Gribkowsky situation.
"Big companies are very wary of being involved in anything that could damage their reputations," said a source.