Engines used by Fiat, Alfa Romeo and Jeep vehicles as well as in CNH Industrial's Iveco trucks have been found to contain potentially illegal engine management software to mask excessive pollution levels, Frankfurt prosecutors said.

The Frankfurt prosecutor's office stopped short of naming Alfa Romeo and Fiat's parent company, Fiat Chrysler, since under German law only individuals, not companies, can be prosecuted.

The investigation targets nine individuals working at an "internatioal carmaker" and seeks to establish their role in putting cars equipped with potentially illegal emissions software on public roads the prosecutor's office said.

A spokesman for FCA said that a number of the group's offices in Europe were visited by investigators in the context of a request for assistance by magistrates in Germany, adding that it was cooperating fully with authorities.

In a similar emailed statement, CNH Industrial confirmed that a number of its offices in Europe have been visited by investigators after a request by German magistrates and that it was cooperating fully with authorities.

FCA and CNH Industrial are both controlled by Exor, the holding company of Italy's Agnelli family.

Potentially illegal software has been detected in the 1.3 litre Multijet and 1.6 litre Multijet engines used in Alfa Romeo, Jeep and Fiat engines as well as in commercial diesel engines used in Iveco and Fiat commercial vehicles, the prosecutors said.

Although these cars passed pollution tests in a laboratory, the cars used software to largely switch off exhaust emissions filtering while driving on the road, they added.

The investigation, which is coordinated by EU justice agency EUROJUST, focuses on nine individuals living in Italy and their activities between 2014 to 2019, they said.

(Reporting by Edward Taylor and Joern Poltz in Germany and Giulio Piovaccari in Italy; Editing by Maria Sheahan, Mark Potter and David Goodman)