Bloomberg News reported Wednesday that the U.S. Department of Justice is preparing to sue Fiat Chrysler Automobiles. Anonymous Bloomberg claimed that the suit could be filed as soon as this week if current discussions fall through.

At the heart of the matter are violations of U.S. clean-air rules involving the VM Motori 3.0-liter diesel engine in 2014, 2015 and 2016 Jeep Grand Cherokees and Ram 1500 pickups.

In January,  the Environmental Protection Agency claimed that FCA sold 104,000 diesel-equipped Grand Cherokees and Ram 1500 pickups that had what the agency called “auxiliary emissions control devices” that were not disclosed, and might be intended to cheat emissions tests. The “devices” are software routines that can disable emissions-control systems during normal operation.

The EPA says FCA has not explained the devices to the agency's satisfaction, while FCA has denied any intent to circumvent emissions regulations. The automaker wrote, by email, that it “...(W)ill defend itself vigorously, particularly against any claims that the company deliberately installed defeat devices to cheat U.S. emissions tests....”