According to a new report, Volkswagen executives were told about the potential financial costs of its diesel emissions cheating a full month before investors were informed.

German newspaper Bild am Sonntag says that VW executive Oliver Schmidt revealed to then chief executive Martin Winterkorn, and others, about the possible financial implications of the cheating on August 25, 2015, indicating costs could reach as high as $18.5 billion.

According to German securities law, companies must inform investors about market sensitive information in a timely fashion, and it wasn’t until September 18, 2015 when the U.S. Environmental Protection Agency publicized the cheating scandal that Volkswagen decided it was time to tell investors.

Autoblog reports that the German conglomerate admitted to using a defeat device to the EPA on September 3, 2015, and chose not to inform investors earlier because board members allegedly thought costs would be “controllable overall with a view to the business activities of Volkswagen Group.”

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