BERLIN/FRANKFURT (Reuters) - German prosecutors imposed a 535 million euro ($598 million) fine on German luxury carmaker Porsche AG, a unit of Volkswagen, as punishment for lapses in supervisory duties which allowed the company to cheat diesel emissions tests.

Prosecutors in the southern city of Stuttgart on Tuesday said that the company’s development department had neglected its legal obligations, which ultimately led to the sale of diesel cars that spewed excessive pollution levels.

The fine against Porsche follows a 1 billion euro penalty for management lapses imposed against Volkswagen by prosecutors in Braunschweig, and a fine of 800 million euros against Audi by prosecutors in Munich, Germany last year.

U.S. authorities disclosed Volkswagen’s systematic emissions cheating on Sept. 18, 2015, sparking the biggest business scandal in the company’s history which has cost Volkswagen Group 30 billion euros in penalties and fines.

VW, Porsche and Audi all sold diesel engine cars which failed to conform to clean air rules and cheated emissions tests.

German prosecutors have pursued individual engineers and took action against the companies for lack of oversight because managers failed to prevent heavily polluting cars from hitting European roads.

Prosecutors said Porsche had not appealed the findings by the prosecutor.

Porsche confirmed the fine and said that prosecutors’ proceedings against the company had come to an end.

The fine does not hinder ongoing proceedings against individual people in relation to Porsche’s diesel manipulations, the prosecutors added.