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FRANKFURT (Reuters) - Munich prosecutors searched the offices of Volkswagen VOWG_p.DE Chief Executive Matthias Mueller as part of an investigation into diesel emission test cheating at Audi, German weekly Bild am Sonntag said.

Some 100 officials searched Audi’s headquarters in Ingolstadt, Germany, and its Neckarsulm plant last week, as well as the Wolfsburg base of Audi’s parent Volkswagen.

Bild am Sonntag said prosecutors targeted 47 VW employees including Mueller and Audi CEO Rupert Stadler, searching personal calendars, notebooks and even memory cards in smartphones.

Mueller was targeted because he is also supervisory board chairman at VW’s premium car unit Audi, Bild am Sonntag said.

Volkswagen was not immediately available for comment.