Germany's top court ruled on July 6 that prosecutors may examine unpublished documents seized from a U.S. law firm in relation to Volkswagen AG's emissions scandal, Reuters reported.

The German automaker hired Jones Day and advisory firm Deloitte to investigate its emissions scandal, which surfaced in September 2015. But the firm's findings were never published by VW apart from a summary for the U.S. Department of Justice.

The ruling will make the unpublished files public as part of any criminal proceedings. Munich state prosecutors said it was not yet clear when they would start to review the files but hoped the documents would make their investigations easier.

Last month, German prosecutors imposed a €1 billion fine on the automaker over its diesel emissions scandal.