A Michigan federal court has charged former Volkswagen Group CEO Martin Winterkorn with defrauding the U.S. for his role in the VW diesel emissions scandal, according to a report from Reuters.

Winterkorn resigned in September 2015, shortly after the company admitted that its 2.0-liter turbodiesel 4-cylinder engine fitted to some VW and Audi models was intentionally and illegally fitted with a defeat device that allowed them to game emissions tests and illegally pollute up to 40 times more than allowed by federal law. It was later learned that VW Group's 3.0-liter V-6 diesel engines also had a similar device.

Thus far, the scandal has cost the company more than $30 billion in buybacks and fines, with more likely on the way in Germany. Two VW executives have been convicted in the U.S. so far, while five others have been charged. A handful of execs have also been arrested in Germany as investigations there take place.

CHECK OUT: How did Volkswagen's diesel defeat device work?

According to Reuters, the charges against Winterkorn were filed secretly in March and only became public on Thursday. They include four felony counts, including conspiracy to defraud the United States, wire fraud and violating the Clean Air Act

The cheating was originally discovered by a lab at West Virginia University.

Winterkorn may never actually face the music in the U.S. because Germany typically does not extradite its citizens for trials outside of the European Union. That doesn't mean he will be safe from prosecution in Germany, though.

Stay tuned as this story develops.