Prosecutors in Stuttgart say they are investigating the chief executive of Volkswagen, Matthias Mueller, in connection with the emissions scandal that erupted at the firm in late 2015.
It is the first time he has been named in connection with official investigations into the affair.
His predecessor, Martin Winterkorn, and the current VW chairman, Hans-Dieter Poetsch, are also under scrutiny.
Mr Mueller became VW chief executive after the scandal broke.
However, at the time he was a board member of Porsche SE, the holding company which owns a majority of voting shares in the Volkswagen Group.
He was also chief executive of the Porsche sports car business, a subsidiary of the VW Group and Porsche SE.
The investigation is not looking into the causes of the scandal itself, but at how the board of Porsche SE, including Mr Mueller, responded to it.
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SOURCE: BBC News