Volkswagen AG (VLKAY) shares were under pressure Wednesday after prosecutors searched the headquarters of its Audi Group division as part of an ongoing probe into the use of 'cheat devices' in diesel emissions engines.

The probe overshadowed the luxury brand's full-year earnings, which showed operating profits had fallen by some 40% last year to just over €3 billion. Reuters, citing a statement from German prosecutors, said the search, which included two Audi plants and its Ingolstadt head office, was focused on the sale of 80,000 cars in the United States between 2009 and 2015.

Audi was the second-largest contributor to VW group sales last year, the company's annual report indicated Tuesday, with 1.5 million units sold and €59.3 billion in revenues generated.

Volkswagen shares were marked 1.57% lower by mid-day in Frankfurt and changing hands at €139.77 each, although the stock has risen some 40% since hitting an all-time low in early October 2015 after news of the emissions scandal first broke.

In a separate event, but one that relates to the broader European response to the "dieselgate" scandal, Renault SA (RNLSY) shares fell sharply Wednesday after a report in France's Liberation newspaper said the carmaker is suspected of trying to disguise the true level of emissions from some of its diesel-powered vehicles.

The paper said that it had consulted documents from France's Directorate-General for Competition, Consumer Affairs and Fraud Prevention which concluded that "the company used a strategy aimed at distorting the results of antipollution tests."

"Important differences between the performance of certain Renault engines in the laboratory and their results under real conditions," were found, the paper said, adding the accusation forms the cornerstone of an investigation reportedly opened by French prosecutors in January.

Renault shares were marked 3.6% lower in Paris at €82.27 each by mid-day and have fallen more than 7% since reports of the emissions investigation first appeared on Jan. 12, compared to a 1.7% gain for the Stoxx All Europe 800 Automobiles & Parts Index.