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.

These devices detected when a car was undergoing emissions testing and altered performance to meet environmental standards — while in real-world driving conditions, the cars emitted pollutants far above legal limits.

In 2017, Volkswagen admitted to manipulating emissions data in the United States, sparking global backlash and triggering one of the biggest corporate scandals in automotive history. The fallout plunged the Wolfsburg-based carmaker into a deep crisis.

In 2019, German prosecutors charged then-CEO Herbert Diess, Chair Hans Dieter Pötsch and former CEO Martin Winterkorn — who resigned shortly after the scandal broke in 2015 — with market manipulation related to the emissions deception.

In 2020, a German court ended legal proceedings against Deiss and Pötsch as VW coughed up a €9 million fine over the scandal.

Winterkorn was originally set to be part of this trial, but was removed for health reasons before it kicked off in September 2021. In his capacity as a witness and defendant, Winterkorn has continued to deny responsibility for the scandal.

Since the scandal erupted, Volkswagen has faced a barrage of lawsuits and legal proceedings. In 2020, the company said that the crisis had cost it more than €30 billion in fines and settlements.