German prosecutors have opened an investigation against Volkswagen's former CEO Martin Winterkorn.

Chief prosecutor Birgit Seel says it aims to find what his role was in the Volkswagen emission scandal.

"Based on public complaints which have been filed we have started an investigation into fraud allegations in relation to the VW emissions scandal. The complaints were against Dr. Martin Winterkorn, so the investigation will seek to determine whether reasonable suspicion exists against him or other employees with positions of responsibility at VW."

Winterkorn denied any wrongdoing on his part and sincerely apologized for what happened.

"To make it very clear: manipulation at VW must never happen again. Ladies and gentlemen, many millions of people across the world trust our brands, our cars and our technologies. I am endlessly sorry that we betrayed the trust. I apologise profusely to our clients, to the authorities and the entire public for the wrongdoing."

Winterkorn has been Volkswagen's CEO since 2007.

He resigned on Wednesday after Volkswagen admitted that 11 million diesel cars might have been involved in the emissions manipulation issue.