The United States Environmental Protection Agency (EPA) has accused car manufacturer Fiat Chrysler of violating diesel emissions standards on more than 100,000 trucks and SUVs sold by the company since 2014.

According to the EPA, Fiat Chrysler made use of software that allowed vehicles to generate excess pollution. The reported use of the undeclared software and the potential increase in admissions would be a violation of rules set by the EPA and the California Air Resources Board.

The supposed engine management tool was present in Jeep Grand Cherokees and Dodge Ram 1500 trucks with 3.0-liter diesel engines produced between 2014 and 2016—a total of more than 104,000 vehicles. The software in the engines reportedly results in increased emissions of nitrogen oxides.

The EPA has not yet determined if the software is considered a defeat device, which its rules define as “an auxiliary emission control device (AECD) that reduces the effectiveness of the emission control system under conditions which may reasonably be expected to be encountered in normal vehicle operation and use.”

The EPA reported it found eight undisclosed pieces of software that can alter how a vehicle emits air pollution.

EPA official Cynthia Giles said in a statement, "Failing to disclose software that affects emissions in a vehicle’s engine is a serious violation of the law, which can result in harmful pollution in the air we breathe."

Fiat Chrysler said it was “disappointed” in the EPA’s decision, according to a statement from the company provided to IBTimes. The company said it plans to demonstrate to the EPA that its emissions controls tools are “properly justified” and not defeat devices.

There are exemptions to the EPA’s ban on emission control devices, including if the device is necessary to help protect the vehicle from damage or accident. Fiat Chrysler believes its software would fall under such a category.

The EPA was led to Fiat Chrysler’s engine software in a probe that branched out from its investigation into German automaker Volkswagen. The company was found to have used defeat devices to cheat emissions tests in more than 580,000 of its diesel vehicles sold in the U.S.

The German manufacturer agreed to buy back many of the cars and pay $4.3 billion in criminal and civil fines. The company pled guilty to three felonies for misleading regulators and selling polluting vehicles.

Fiat Chrysler holds that its case is not similar to the Volkswagen incident. "There is nothing in common between the VW reality and what we are describing here," Company CEO Sergio Marchionne said on a press call. He called any potential comparison of the companies is "absolute nonsense" and said anyone who disagrees with him is "smoking illegal material."

Despite the aggressive stance of Fiat Chrysler’s CEO, who derided the EPA for what he called an “incredibly belligerent” attack on automakers, the company said it intends to “work with the incoming administration to present its case and resolve this matter fairly and equitably.”

Scott Pruitt, President-elect Donald Trump’s nominee to head the EPA, will likely have a less aggressive stance toward the potential violation. He has described himself as the “leading advocate against the EPA’s activist agenda,” though as the attorney general of Oklahoma, Pruitt did sue Volkswagen over false advertising of its diesel vehicles.