Authorities in nearby Braunschweig said Thursday's raids were aimed at securing "documents and data storage devices" to help them identify anyone involved in the manipulation of emissions software in VW's diesel cars.

German news agency DPA reported searches were also carried out at private locations including the apartments of some VW employees. It did not say whose dwellings had been targeted.

According to a statement, three prosecutors executed the searches with the help of officials from the German state of Lower Saxony's office of criminal investigation. An investigation into the suspected fraud at Europe's largest automaker was launched last week.

Perfect timing

The raid came on the same day that Germany's vice chancellor and economy minister, Sigmar Gabriel, was in Wolfsburg to attend a meeting of VW employee representatives.

At the meeting, Gabriel urged VW to be proactive while resolving the cheating scandal.

"It is clear that the company must clear this up. The more offensively it does so, the better," Gabriel said. "The more defensively it approaches the question, the more difficult it will be."

Martin Winterkorn, VW's long-standing CEO who ran the company for nearly nine years, stepped down soon after it was revealed that the auto concern had deliberately manipulated emissions data. So far, four other individuals, including three managers tasked with engine development, have also been suspended.

A VW executive testifies

Also on Thursday, VW's top US executive, Michael Horn, appeared before a subcommittee in Congress to answer questions about the on-board computer software the company installed in about 11 million diesel-powered cars to trick emissions tests.

In his testimony, Horn swore he had no prior knowledge of the so-called "defeat devices."

cjc/hg (AP, Reuters, dpa)