Enlarge / Wolfgang Hatz, head of development at Porsche AG, speaks during a presentation to announce the expansion of the luxury automaker’s research and development center in Weissach, Germany on Friday, July 18, 2014. Photographer: Martin Leissl/Bloomberg via Getty Images (credit: Getty Images)

On Thursday, Wolfgang Hatz, former engine chief for Volkswagen and Audi and later the head of research and development at Porsche, was arrested in Munich. With Hatz’s arrest, the slow-moving investigations of Volkswagen Group in the aftermath of the 2015 emissions scandal seem to be gathering momentum, according to reports from German paper Süddeutsche Zeitung and the New York Times.

The news comes by way of anonymous sources, as German privacy law prohibits the government from disclosing the identities of suspects. German authorities confirmed to the New York Times that a suspect was arraigned on Thursday morning in connection with the ongoing investigation of VW Group’s Audi unit.

Hatz was the engine chief at Audi between 2001 and 2007, right around the time that the company began implementing a software-based “acoustic condition” workaround for its diesel engines. According to court filings and academic research, Audi allegedly wanted to get rid of the rattling noise that some diesel engines make on startup, so it created software to inject extra fuel into the engine on ignition. The company then worked to mask the extra emissions created by this fix, and from there, the emissions cheating software apparently grew as the company demanded different and increasingly hard-to-achieve features for its diesel engines. There’s evidence that the Audi software was then borrowed by Volkswagen for its line of diesels, which were aggressively marketed as “clean diesel cars” in the US.