Audi confirmed on Monday that its R&D chief Stefan Knirsch is stepping down from his position with immediate effect.

The news follows a September 16 report from German newspaper Donaukurier that Knirsch would be leaving the automaker as he may have been aware of the diesel emissions cheating at a handful of Volkswagen Group brands, including Audi, well before it became public in 2015.

Fellow German publication Focus reported September 18 that American law firm Jones Day, which has been hired by the Volkswagen Group to get to the root of the emissions cheating, has proof that Knirsch knew of the cheating and gave a false statement of his knowledge on the matter.

Knirsch was appointed Audi R&D chief on January 1, 2016. He replaced veteran engineer Ulrich Hackenberg who was one of nine senior VW Group executives suspended after the discovery of the emissions cheating. Following the scandal, the VW brand lost its R&D chief Heinz-Jakob Neußer, while Porsche lost Wolfgang Hatz.

There have been claims Audi CEO Rupert Stadler may also have been aware of the cheating, though Reuters, citing three sources, reported on September 23 that no evidence had been found against him.

While the VW Group has reached a settlement in the United States over its 2.0-liter diesel engine, a settlement hasn't yet been announced for 85,000 cars sold with larger 3.0-liter V-6 diesel engines that also cheated on emissions. The V-6 diesels affect models from Audi, Porsche and VW.