German prosecutors raided Volkswagen's headquarters in Wolfsburg in northern Germany investigating the manipulation of diesel emissions. VW said it had handed over a "comprehensive" range of documents to investigators.
Last week it emerged that the company had been fitting software on diesel engines designed to cheat emissions testing. In a statement, prosecutors said the aim of the raids was to "secure documents and data storage devices" that could identify those involved.
The searches came as Michael Horn, the US boss of VW, apologised before a US congressional committee.
"On behalf of our company, my colleagues in Germany and myself, I would like to offer a sincere apology for Volkswagen's use of a software programme that served to defeat the regular emissions testing regime.
"We have broken the trust of our customers, dealerships and employees, as well as the public and regulators."
VW has suspended four members of staff over the scandal, which could lead to 11 million VW, Seat, Skoda and Audi vehicles being recalled worldwide.