Fiat Chrysler (FCAU) - Get Report  shares extended declines in early European trading Wednesday after the U.S. Department of Justice said it is suing the Italian-American automaker over illegal emissions' management technology found in its vehicles.

The DoJ has filed a civil complaint alleging that Fiat failed to disclose engine management software found in its vehicles, at the certification stage, and that the engine feature in question does constitute a so called defeat device. Defeat devices are designed to mislead regulators over the true emissions' output of an engine when vehicles are tested in lab conditions.

Fiat stocks slid more than 3% during at the start of trading to change hands at an intraday low of €9.15, reducing its year to date gain to a little over 7%, before paring that decline to around 1.6% and a price of €9.34. The Stoxx Europe 600 Auto & Parts index was quoted just more than 1% lower shortly after the opening bell.

Volkswagen (VLKAY) was found to be guilty of having installed such software in its vehicles, back in 2016, prompting the German automaker to agree a near $20 billion settlement with U.S. justice officials.

"The complaint alleges that FCA equipped nearly 104,000 Ram 1500 and Jeep Grand Cherokee vehicles sold in the United States with at least eight software-based features that were not disclosed in FCA's applications for certificates of conformity and that affect the vehicles' emission control systems," the DoJ said in a statement.

Reports of a possible complaint first emerged back in January when the Environmental Protection Agency flagged undisclosed software in some Fiat Chrysler vehicles.

Fiat stock fell by around 15% in the days after the announcement only to pare losses, before eking out a high single digit gain for the year to date. 

The DoJ said at the time that it would investigate whether the software constitutes a defeat device, adding that "in short, the complaint now alleges that the vehicles contain defeat devices."