Continental said it is cooperating with authorities.
The Hanover prosecutor's office could not be reached for comment.
In July prosecutors in Hanover searched Continental, investigating its role in supplying engine components for a 1.6 litre VW diesel engine which had breached emissions limits and masked excessive pollution using illegal software.
At the time, prosecutors searched premises in Hanover, Regensburg, Wolfsburg, Gifhorn, Berlin, Frankfurt and Nuremberg and investigated employees of Continental for abetting fraud and for providing false documentation.
Continental late on Wednesday warned it would post a third-quarter loss when it reports financial results on Nov. 11.
(Reporting by Jan Schwartz and Joern Poltz; Writing by Edward Taylor; Editing by Maria Sheahan)