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Gerry Lauzon/Flickr CC by 2.0

Today, the United States Justice Department filed a lawsuit on behalf of the Environmental Protection Agency (EPA) against Volkswagen, saying that the car company had violated the Clean Air Act by installing software on their cars that allowed them to circumvent emission regulations.

This all started back in September when the EPA announced that they had discovered software that allowed Volkswagen cars to cheat emissions tests, running clean in the lab while in testing mode, and then switching back to a high-performance (and much dirtier) mode once on the road. The software affected 600,000 cars in the United States and the problems just seem to keep expanding. Cars in other countries are also affected.

The car emissions that violate the Clean Air act include nitrogen oxides (NOx), and fine particles that can get into the lungs, affecting people’s ability to breathe.

From the EPA:

“Car manufacturers that fail to properly certify their cars and that defeat emission control systems breach the public trust, endanger public health and disadvantage competitors,” said Assistant Attorney General John C. Cruden for the Justice Department’s Environment and Natural Resources Division said in a statement. “The United States will pursue all appropriate remedies against Volkswagen to redress the violations of our nation’s clean air laws alleged in the complaint.”

The lawsuit focuses on several Volkswagen subsidiaries, listing Volkswagen AG, Audi AG, Volkswagen Group of America Inc., Volkswagen Group of America Chattanooga Operations LLC, Porsche AG and Porsche Cars North America Inc as defendants. As the Associated Press notes, other criminal charges or other civil lawsuits from owners may follow.