BERLIN (AP) — Former Volkswagen CEO Martin Winterkorn is testifying before a German parliamentary inquiry in his first public appearance since he resigned in the wake of the company's diesel emissions scandal.

Winterkorn, flanked by two lawyers, told the panel Thursday "it is not the case" he knew earlier than previously thought of the scandal. He said he's still seeking "satisfactory answers" as to what happened.

The 69-year-old quit in September 2015, several days after news of Volkswagen's use of software to cheat on emissions emerged in the U.S. He told the panel "as CEO I took political responsibility" — echoing previous statements.

He added: "Believe me, this step was the most difficult of my life."

Winterkorn said he wouldn't comment on details that are a matter for a criminal investigation in Germany.