German prosecutors have raided Audi and VW sites as part of a probe into the manipulation of US emissions tests.
The searches were carried out in order to identify those involved in installing the devices that cheated the diesel tests, Munich prosecutors said.
Audi-owner VW has already agreed to settlements of $21bn (£17bn) in the US.
The raid at Audi's sites coincided with the company's annual press conference, in which it reported pre-tax profits of 3bn euros (£2.6bn) for 2016, a 37% drop on the previous year. The firm also announced a new autonomous vehicles division.
In a statement, Audi said it was co-operating with authorities.
In September 2015, Audi admitted that more than two million of its cars were fitted with software that allowed for the manipulation of test.
Prosecutors from three German states said the raids were in connection to some 80,000 V6 3.0-litre diesel cars sold in the US between 2009 and 2015, whose buyers were unaware of the emissions scandal.
They added that the search warrants were carried out particular to "clarify which people were involved in applying the [manipulation] technology and in providing false information to third parties".