The US Justice Department on Monday filed an environmental lawsuit against Volkswagen over the automaker's cheating on emissions standards in diesel vehicles.
The civil complaint was filed in federal court in Detroit against the German company on behalf of the US Environmental Protection Agency (EPA).
The Justice Department said the lawsuit was the first stage in bringing Volkswagen to justice for failing to disclose that the vehicles were equipped with a device designed to defeat emissions tests conducted in the United States.
"The alleged misrepresentations allowed almost 600,000 diesel engines to emit excessive air pollution across the country, harming our health and cheating consumers," said US Attorney Barbara L McQuade for the Eastern District of Michigan.
A spokesman at the company's headquarters in Wolfsburg, Germany, told dpa that Volkswagen did not know the details of the complaint, but would now examine them, adding that VW is in a constant contact with authorities.
"We are working on solutions, but cannot speak publicly about the details," the spokesman said.
VW already is threatened with penalties that could amount to billions of dollars. The group acknowledged the use of manipulation software in September shortly after the scandal erupted.
The lawsuit filed Monday alleges that the vehicles had defeat devices that impaired their emission control systems. The devices masked the cars' actual emissions, which in fact exceeded EPA’s standards, resulting in harmful air pollution, the Justice Department said in a release.
The complaint also alleges that Volkswagen violated the Clean Air Act by selling vehicles that were designed differently from what Volkswagen had stated in applications for certification submitted to the EPA and the California Air Resources Board (CARB).
"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," Assistant Attorney General John C Cruden said in the statement.
The Justice Department called the filing "an important step to protect public health by seeking to hold Volkswagen accountable for any unlawful air pollution."
The Justice Department also said discussions on a recall have not produced an "acceptable way forward," but said the talks would continue in parallel with the lawsuit, which also names VW subsidiaries Audi and Porsche.
The automaker said last month it was preparing a recall of around 11 million diesel vehicles fitted with manipulative software designed to spoof emissions standards testing.
In Germany, a recall of affected vehicles will start this year, the company has said.
The company has announced structural changes to management as a result of the emissions scandal. It also has suffered a sharp dive in its share price and a blow to its reputation.