U.S. officials announced charges against a former manager with Audi - a high-end brand in the Volkswagen group - who directed employees to design software to cheat U.S. emission tests.
The devices allowed the cars to spew up to 40 times the permissible limits of nitrogen oxide during normal driving, but this was hidden during emissions testing.
VW faces an array of legal challenges in Germany and worldwide relating to the software, installed mainly in own-brand vehicles but also in cars made by Audi, Skoda and Seat, among its stable of 12 brands.
Pamio, who formerly headed a division within Audi's diesel engine department in Germany, led a team of engineers responsible for designing emissions control systems for diesel vehicles in the United States between 2006 and late 2015.
According to the statement, "Pamio directed Audi employees to design and implement software functions to cheat the standard U.S. emissions tests.
"Pamio and co-conspirators deliberately failed to disclose the software functions, and they knowingly misrepresented that the vehicles complied" with U.S. emissions standards.
In total, Volkswagen has agreed to some $23 billion in payments in the United States to compensate some 600,000 U.S. car owners. Volkswagen previously pleaded guilty to three felony counts connected to the cheating scandal, and in April was ordered to pay a $2.8 billion fine.
U.S. authorities made their first indictment of a Volkswagen employee in the "dieselgate" scandal in September 2016. The accused U.S. engineer pleaded guilty to avoid a lawsuit.
Six other company executives have since been implicated, one of whom was arrested in January in Miami.