Stadler, who had his contract extended last year, has been named a suspect by the Munich prosecutor’s office alongside another unnamed member of Audi’s board of management, according to Reuters.
Audi admitted to having used illegal defeat devices to manipulate its cars’ emissions in November 2015; Stadler has been CEO since 2007. It is thought that 11 million VW Group cars have been fitted with emissions manipulation devices.
As part of the probe, Stadler’s home has been raided, while authorities are currently investigating 19 other suspects, the identities of whom have not been disclosed.
Stadler was summoned to court in Stuttgart recently to give evidence at an emissions scandal hearing, alongside former VW Group boss Martin Winterkorn, former Audi technical director Ulrich Hackenberg and other prominent current and former VW Group executives.
Autocar is awaiting comment from Audi.