A French prosecutor has opened an investigation into Fiat Chrysler (FCAU) - Get Report regarding allegations the automaker cheated diesel emission tests, a judicial source told Reuters.

"I can confirm that a judicial investigation has been opened into aggravated cheating," the source said.

The company has taken note of the investigation and said that its diesel vehicles sufficiently comply with emission regulations, as confirmed by the Italian Transport Ministry, a Fiat spokesman said.

The company will continue to cooperate with the authorities on all investigations and is confident the matter will be resolved, the spokesman added.