The U.S. government has filed a civil lawsuit against automaker Fiat Chrysler, saying the company has used illegal software to fake emission results on its diesel vehicles.

The civil complaint filed Tuesday follows initial accusations from the Environmental Protection Agency released in January.

The software reportedly hid emissions of nitrogen oxide, allowing the vehicles to appear to comply with regulations set forth in the Clean Air Act, while still emitting more of the gas than is allowed.

At issue are the 2014 to 2016 models of Grand Cherokees and Dodge Ram 1500 pickup trucks with three-liter diesel engines sold in the United States, around 104,000 vehicles in total, the EPA said.

In 2015, Volkswagen was caught using a similar device to cheat emissions standards. Volkwagen, however, admitted to having cheated, while Fiat Chrysler denies wrongdoing. The VW scandal eventually led to approximately $20 billion worth of fines levied against the company and indictments of seven company executives.

Fiat Chrysler did not immediately comment Tuesday, but its shares fell 2.9 percent.

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