Fiat Chrysler Automobiles (FCA) was allowed to skip tests in Italy's emissions-cheating investigation, according to a report from Italy's transport ministry.
The tests, designed to find illegal engine software, were completed by BMW, Ford, Mercedes-Benz, Volkswagen and General Motors but three of the seven FCA models tested didn't record results, according to Reuters.
The three models were a Jeep Cherokee 2.0, Alfa Romeo Giulietta 1.6 and Lancia Ypsilon 1.3, but transport ministry spokeswoman Luisa Gabbi told Reuters more results for FCA models would follow and added that "no key test has been omitted for FCA". FCA also denies breaking any laws.
The news has led to calls for the relationships between national testing authorities and domestic car makers to be scrutinised more closely ahead of a vote on Thursday on tougher EU control of vehicle testing conducted by national authorities.
Prosecution in France
FCA could still face prosecution in France after investigators recorded abnormal emissions of nitrogen oxide (NOx) pollutants from some of its diesel engines.
The investigation allegedly revealed emissions from some of the manufacturer's models were several times higher than regulatory limits, and FCA has been referred for possible prosecution while investigations into other car brands continue. Both Volkswagen and Renault have previously been referred to French prosecutors.
Results from a testing programme carried out by French regulators last July showed that the Jeep Cherokee emitted eight times the NOx limit during lab tests, while the Fiat 500X emitted almost 17 times the limit in road testing, according to the report.