The U.S. Department of Justice indicted four Audi AG managers for their roles in a conspiracy to cheat U.S. emissions tests with certain 2009-2015 Audi models equipped with a 3.0-liter V6 TDi diesel engine.

The indictments were filed yesterday in a U.S. District Court in Detroit, although hearings in the case have not been set and lawyers for the four German execs couldn’t be immediately identified, as reported by Autonews.

Indicted in the matter were Richard Bauder, the former head of Audi’s diesel engine development department in Neckarsulm, Axel Eiser, head of Audi’s engine development division in Ingolstadt (2008-2013), Stefan Knirsch, who took over for Eiser between 2013 and 2016 and Carsten Nagel, head of engine registration in Neckarsulm.

Each of them has been charged with felonies such as conspiracy to defraud the U.S. government, violation of the Clean Air Act and wire fraud. However, getting them into U.S. custody is easier said than done seen as how the German constitution protects German nationals from extradition.

The indictments cover the design as well as the certification of five specific Audi models: 2009-2015 Q7, 2014-2015 A6 and A7, 2014-2015 A8L and the 2014-2015 Q5. The 2009-2015 VW Touareg also falls under the same category since it was powered by the 3.0-liter TDI diesel unit in question.

Meanwhile, U.S. prosecutors allege that Audi’s engine development engineers warned their superiors that these vehicles needed larger tanks of AdBlue Diesel Emission Fluid in order to comply with emissions regulations, yet such measures would have conflicted with other program requirements imposed by Audi, such as mandates that the vehicles would have a “10,000 mile AdBlue refilling interval”, as well as a “large trunk and high-end sound system.”