Now that both the Environmental Protection Agency and the California Air Resources Board (CARB) have accused Fiat Chrysler of using “defeat device” software to skirt emission standards in more than 100,000 vehicles, the Department of Justice is expected to file a lawsuit against carmaker. 

Reuters, citing people familiar with the matter, reports that the Justice Department could file a lawsuit against FCA as early as this week if regulators fail to reach an agreement with the carmaker to resolve allegations it illegally used undisclosed software that allowed the vehicles to spew diesel emissions in excess of federal standards.

The possible lawsuit would be the result of the DOJ’s ongoing investigation into the carmaker, which found emails related to engine development and emissions, according to the sources.

The lawsuit against FCA would likely be filed by May 24, the date a federal judge in California is expected to hold a hearing on several lawsuits filed by owners of the carmakers’ vehicles.

A rep for FCA tells Reuters that any litigation related to the emissions issues would be “counterproductive” to its work with the EPA and CARB.

However, if a lawsuit is filed, the company says it will “defend itself vigorously.”

FCA’s emission issues came to light in January when the EPA and CARB accused the company of equipping more than 104,000 diesel-engine SUVs and trucks made and sold since 2014 with hidden software that could have compromised the vehicles’ emissions control systems.

The notice of violation of the Clean Air Act covered model year 2014 to 2016 Jeep Grand Cherokees and Dodge Ram 1500 vehicles with 3.0 liter diesel engines.

According to the EPA, these vehicles use software that could allow them to emit levels of nitrogen oxide (NOx) in excess of standards set by the Clean Air Act.

The auxiliary emission control devices, which could be similar to the defeat devices used in 500,000 VW and Audi vehicles in the U.S. and 11 million worldwide, were first uncovered by the EPA after the agency expanded a testing program to screen for defeat devices in light duty vehicles.

The testing — performed sometime after Sept. 2015 — revealed that the FCA vehicles produce increased NOx emissions under conditions that would be encountered in normal operation and use. As part of the investigation, EPA found at least eight undisclosed pieces of software that allow emissions controls to be used at full force during lab testing, but reduced when cars on undergoing regulator use.

By failing to disclose the software during certification and then selling vehicles that contained it, FCA violated important provisions of the Clean Air Act, the agencies alleged.

In February, Reuters reports, FCA revealed that it had received subpoenas from federal and state authorities related to information about the diesel emission issue.

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