German authorities have detained the chief executive of Volkswagen’s Audi division, Rupert Stadler, as part of a probe into manipulation of emissions controls.

The dpa news agency said Volkswagen confirmed reports that Stadler was detained Monday.

Munich prosecutors searched Stadler’s private residence last week in their investigation of suspected fraud and indirect improprieties with documents. A total of 20 people are under suspicion in the probe.

The probe of Stadler focuses on cars sold in Europe that were believed to be equipped with software which turned emissions controls off during regular driving.

Volkswagen has pleaded guilty to criminal charges in the United States. Two managers are serving prison terms in the United States.

Top image: In this Thursday, May 3, 2018 file photo, Rupert Stadler, CEO of Audi AG, attends the shareholders’ meeting of the Volkswagen stock company in Berlin, Germany.  (AP Photo/Michael Sohn)