Wolfgang Hatz has been released under a set of strict conditions.

Ex-Volkswagen, Porsche and Audi research and development chief, Wolfgang Hatz, has been released from pre-trial detention under a strict set of conditions designed to stop him fleeing Germany.

According to reports in the Süddeutsche Zeitungthe ex-engine boss was bailed for €3 million ($4.7 million) earlier this week. Along with that hefty sum, Hatz was forced to relinquish his passport, and has been ordered not to contact other accused parties or witnesses to the case.

He's been in jail for almost nine months, with German prosecutors accusing him of obstructing their investigation, and refusing to give testimony. Lawyers for the executive have been appealing his detention since the arrest, with the Munich Appeals Court finally bailing him this week.

Hatz was head of research and development at Porsche at the time of his arrest, having previously occupied the same role at Volkswagen and Audi.

The news comes after Audi CEO, Rupert Stadler, was arrested last week over potential evidence suppression.

"As part of an investigation into diesel affairs and Audi engines, the Munich prosecutor's office executed an arrest warrant against Professor Rupert Stadler on June 18," the Munich prosecutor's office said in a statement.

A judge ordered he be kept in detention, to reduce his risk of damaging the investigation.

German media has suggested the Munich public prosecutor was concerned Stadler was getting ready to meet – and potentially collude – with other Audi executives implicated in the scandal.

MORE: Dieselgate scandal coverage