Weekly Bild am Sonntag reported on Sunday that the KBA had found reliable evidence that exhaust gas treatment in some models of diesel car made by PSA Group's Opel division shuts down during driving.

"Before the outcome of this hearing, nothing conclusive can be said about the inadmissibility of the defeat device," a spokeswoman for the ministry said.

Some 60,000 Opel cars worldwide of model lines Cascada, Insignia and Zafira equipped with the latest Euro-6 emissions standard are affected by the issue, 10,000 of which are in Germany where Opel is based, the newspaper reported.

The affected models' emissions of nitrogen oxides (NOx) exceeded statutory limits more than tenfold, it said.

An Opel spokesman said in an email responding to the Bild am Sonntag report that the company had "already in December 2015 recognised the potential for improvement and started a technology initiative to raise transparency, credibility and efficiency for the benefit of customers".

(Reporting by Arno Schuetze; Editing by Catherine Evans)