A German regional court on Monday convicted four former Volkswagen executives of fraud in connection with the long-running Dieselgate emissions scandal.

The court sentenced two of the former executives to prison for several years, while the remaining two received suspended sentences. The ruling concludes a major trial that spanned nearly four years.

The scandal known as Dieselgate first came to light in September 2015, when the U.S. Environmental Protection Agency discovered that many diesel vehicles produced by German carmaker Volkswagen were equipped with illegal so-called defeat devices.