A member of Volkswagen's supervisory board says he expects further resignations at the German automaker in the wake of the scandal over rigged U.S. emissions tests.

Olaf Lies, economy and transport minister of VW's home state Lower-Saxony, which holds a 20 percent stake in the company, said the investigation into the scandal was only just starting.

He told rbb-Inforadio Thursday that "there must be people responsible for allowing the manipulation of emission levels to happen."

Lies spoke a day after Volkswagen CEO Martin Winterkorn resigned, saying he took responsibility for the "irregularities" found by U.S. inspectors in VW's diesel engines while insisting he'd personally done nothing wrong.

VW has filed a criminal complaint with German prosecutors seeking to identify those responsible for any illegal actions in connection with the scandal.