The war between Fiat Chrysler Automobiles and the Environmental Protection Agency recently escalated, but newly released documents reveal the battle has been brewing since 2015.

According to e-mails attained by Reuters, the EPA informed FCA it suspected the company had used a defeat device in some of its models. The company set up a meeting with the EPA in November 2015 and the government agency revealed there was a least one auxiliary emissions control device that appeared to violate regulations.

After a couple of month, the director of the EPA’s Transportation and Air Quality Compliance Division e-mailed FCA North America’s Head of Vehicle Emissions, Certification, and Compliance to ask for a conference call. As Jalopnik reports, the email sent by Byron Bunker said: “I am very concerned about the unacceptably slow pace of the efforts to understand the high NOx emissions we have observed from several [redacted] vehicles with the [redacted].” The redacted words are believed to be “diesel-powered” and “3.0-liter EcoDiesel engine” or some variation of them.

FCA’s Head of Vehicle Safety and Regulatory Compliance followed up with the EPA a few days later: “As I am sure you can appreciate, conclusions regarding possible noncompliance of FCA’s engine design, as violating EPA’s ‘defeat device’ regulations, are conclusions of a legal nature with potentially significant regulatory and commercial consequences.” Mike Dahl went on to ask the EPA to hold off on making any conclusions before the company could fully explain its emissions strategy.

Last month, FCA presented a proposal to install updated emissions software on 2014-2016 Jeep Grand Cherokee and Ram 1500 vehicles equipped with diesel engines. The company also filed an application for a diesel vehicle emissions certification on the 2017 Grand Cherokee and Ram 1500 EcoDiesel.

The proposal apparently didn’t cut it with the authorities, as the United States Department of Justice and the EPA both sued the automaker a few days later, claiming 104,000 vehicles equipped with the 3.0-liter diesel engine have a defeat device as well as “software functions” that were not disclosed during the certification process.

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