WASHINGTON • Two other major carmakers have come under scrutiny in connection with cheating in meeting emissions standards.

French prosecutors yesterday said they were investigating Renault, hours after the United States Environmental Protection Agency (EPA) accused Fiat Chrysler of installing secret software that allowed more than 100,000 of its diesel vehicles to emit pollutants above legal levels.

Paris prosecutors opened the preliminary probe into emissions by Renault vehicles weeks after fraud watchdogs said their research found enough material to require further investigation.

The cases have echoes of one against Volkswagen, which on Wednesday pleaded guilty to criminal conspiracy as part of an emissions-cheating scheme. In both the Fiat Chrysler and Volkswagen cases, the governments focused on software in vehicles that can adjust emissions levels.

Commenting on the Fiat Chrysler case, Ms Cynthia Giles, an assistant administrator at the EPA, said the software resulted in excess emissions of nitrogen oxides, which have harmful health effects. While she stopped short of describing the software as a defeat device of the sort used by Volkswagen to cheat on emissions tests, she said there was no doubt Fiat Chrysler's software "is contributing to illegal pollution".

Mr Sergio Marchionne, chief executive of Fiat Chrysler, denied the company had intentionally broken the law. "There's not a guy" at the carmaker "who would try something as stupid" as cheating on emissions tests, he told reporters. "We have done, in our view, nothing that is illegal."

The 104,000 affected vehicles include the light-duty model year 2014, 2015 and 2016 Jeep Grand Cherokees and Dodge Ram 1500 trucks with 3-litre diesel engines sold in the US, the EPA said.

At issue is software installed in all modern diesel vehicles that calibrates an engine's performance and controls emissions levels. Federal regulations allow diesel cars to shut off emissions controls in certain situations - to protect an engine from overheating, for example.

The EPA believes the software in the Fiat Chrysler cars caused emissions controls to shut down in too many situations - including normal driving conditions - essentially making it function like a defeat device. The company, however, said it had spent months responding to questions from federal regulators and had proposed remedies to address their concerns.

NYTIMES, BLOOMBERG