PARIS -- French officials found that some cars it tests had higher CO2 and NOx emissions on than road than in laboratory tests but found no "cheat" devices.
France's environmental regulator began randomly testing vehicles to check differences between lab results and real-world emissions after Volkswagen Group rigging diesel engines 11 million diesel cars sold worldwide to fool lab tests for health-harming NOx emissions.
"Tests conducted in France on 52 vehicles from 15 different brands showed no cheating device. However, the tests highlighted significantly higher emissions [in CO2 and NOx] in real traffic conditions," the ministry said on Thursday.
The ministry said the vehicles were made by Renault, Fiat Chrysler Automobiles, Mercedes-Benz, Volkswagen, PSA Group, Nissan, Opel and Ford.
Earlier this month, investigators raided five PSA Group offices in France following "anomalies" in emissions tests. PSA said its vehicles comply with pollutant emissions in all countries where it operates.
In January, shares in Renault fell sharply on news that it had been raided by French regulators. Renault said its cars comply with test regulations.
The EU will introduce real driving emissions testing starting September 2017, although some pollution above official limits will be tolerated to allow carmakers to adapt.
Reuters contributed to this report