Frankfurt am Main — German prosecutors said on Tuesday that they have charged three Volkswagen (VW) managers and three employees with fraud as part of their investigation into the huge “dieselgate” emissions-cheating scandal.

Brunswick prosecutors accuse the six of knowingly duping customers in Europe and the US into buying diesel cars rigged with “illegal software” to make them seem less polluting than they actually were.

The six face charges of “serious fraud, indirect falsification of certificates and tax fraud” related to actions between 2006 and 2015, the prosecutors said in a statement.

German prosecutors are investigating dozens of current and former employees over the scandal that erupted in September 2015 when VW admitted to installing software in 11-million diesel-powered vehicles worldwide to skew emissions tests.

The “defeat” devices allowed some cars to spew out up to 40 times more harmful nitrogen oxide than legally allowed.

A total of 11 people have now been formally charged over the cheating by German prosecutors, including former VW CEO Martin Winterkorn who stepped down days after the scandal broke. The former CEO of VW’s luxury Audi subsidiary, Rupert Stadler, has also been charged with fraud, falsifying certifications and illegal advertising.

The Brunswick prosecutors said the six latest suspects helped bring vehicles to market that were wrongly certified. Additionally, in Germany, certain vehicles unlawfully benefited from tax rebates for being assigned the Euro six rating reserved for the newest and, in theory, least polluting diesel engines.

Three of the accused are executives alleged to have played an active role in the scam, while the three other employees “are accused of helping” with the fraudulent acts.

“In particular, they were knowingly and willingly involved in the development, refinement and improvement of the manipulating software,” the statement said.

More than four years after “dieselgate”, the VW group, which includes the Porsche, Seat and Škoda brands, remains mired in legal woes at home and abroad. The scandal has so far cost the car behemoth over €30bn in fines, buybacks and compensation — including a huge settlement with about 600,000 car owners in the US.

Earlier this month, VW said it would open talks to possibly settle a mass lawsuit in Germany brought by some 400,000 duped diesel owners.