German prosecutors have searched the offices of the U.
S. law firm hired by Volkswagen to investigate its diesel emissions test cheating, as they step up their efforts to identify those involved in the scandal.
Europe's biggest carmaker condemned the search, carried out on Wednesday but reported on Thursday, as "unacceptable in every way" and said it would use every legal step to defend itself.
The law firm, Jones Day, declined to comment. The Munich prosecutor's office was not immediately available for comment.