Last week, EU staff had “conducted an inspection” at BMW’s Munich offices, BMW carmaker said in a statement to Reuters, adding that it is “assisting the European Commission in its work”. Earlier this summer, the antitrust officials said they were investigating collusion among German carmakers in response to a tip-off after Der Spiegel magazine reported that Daimler, BMW, Volkswagen and its Audi and Porsche arms conspired to fix prices in diesel and other technologies over decades.

Now Reuters reports that the investigation moved over at VW and Daimler. On Friday, Daimler revealed that it had claimed whistleblower status to avoid any fines. By Monday, investigators were searching offices at Daimler and examining documents at Volkswagen’s headquarters in Wolfsburg and at its Audi in the southern German city of Ingolstadt, spokespeople at Daimler and VW said.

The EU Commission has declined to provide details on its investigation, saying only it had “concerns that several German car manufacturers may have violated EU antitrust rules prohibiting cartels and restrictive business practices.”

It said the searches were an early step in its investigation and did not mean that any of the companies it had inspected had been found guilty of anti-competitive behavior.