Jones Day, a secretive firm with close ties to the current U.S. president, saw its offices in Germany raided Wednesday by local prosecutors investigating its client, Volkswagen AG.

The move by prosecutors in Munich, which came two days before German Chancellor Angela Merkel was due to arrive in the U.S. for a meeting with President Donald Trump, was called “unacceptable” and a “clear violation of legal principles” in a statement by Volkswagen.