The public prosecutor’s office in Munich said on Wednesday that it had filed charges against former Audi chief executive Rupert Stadler. He is being investigated for his role in Volkswagen’s emissions test cheating scandal.

Three other defendants have been accused of having developed engines used in Audi, Volkswagen and Porsche branded cars that used emissions-cheating devices. They are being charged with false certification and criminal advertising practices, prosecutors said, declining to identify the defendants.

Several people familiar with the proceedings told Reuters that the accused include former Audi and Porsche manager Wolfgang Hatz, as well as two engineers.

“Defendant Stadler is accused of having been aware of the manipulations since the end of September 2015, at the latest, but he did not prevent the sale of affected Audi and VW vehicles thereafter,” the prosecutor’s office said in a statement.

The ex-head of Volkswagen’s luxury arm Audi, Stadler was arrested in mid-June 2018 as part of a broader probe into emissions cheating, and has spent several months in prison. In October Volkswagen terminated its contract with Stadler. Audi agreed to pay an €800 million ($891 million) fine in Germany to settle the probe.

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The dieselgate scandal stretches back to 2008, when German auto giant Volkswagen (VW) started selling vehicles with test-rigging software in the UK. The so-called “defeat devices” had been installed into 11 million cars worldwide. In 2015, VW acknowledged using illegal software to cheat US emissions tests on diesel engines.

The disclosure triggered outrage across the world, dragging the automaker into the biggest crisis in its history. VW has been hit with over €30 billion ($33.5 billion) in costs relating to dieselgate, much of it for fines, buybacks and compensation payouts in the US.

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The scandal led to a massive regulatory crackdown across the entire car-building sector and forced VW to make a massive shift to electric vehicles.

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