Volkswagon's former CEO, Martin Winterkorn, has come under investigation by the German state attorney.
The German state attorney's office in Braunschweig, not too distant from Volkswagen's base in Wolfsburg, acknowledged that it had received complaints from people who had raised the issue anonymously, reported the New York Times.
The investigation is seeking to clarify the criminal nature of the emissions issue, specifically whether it may constitute fraud and to determine who knew about it.
It comes after a terrible couple of days for Winterkorn, as he saw the US Environmental Protection Agency issue their j'accuse regarding software which allowed the machine to dodge clean-air standards.
In particular, the EPA said it had found that four-cylinder diesel VWs and Audis sold in the US since 2008 came loaded with software which "detects when the car is undergoing official emissions testing, and turns full emissions controls on only during the test".
Winterkorn resigned on Wednesday while repeatedly denying any knowledge of the software.
Volkswagen's supervisory board has corroborated Winterkorn's statement that he was unaware of the "defeat device" and added that the company had additionally asked the German attorneys, following his resignation, to investigate the possibility of employee criminal behaviour. ®