Fiat is under investigation by German authorities trying to establish whether the car maker has been running a system that manipulates European laboratory emissions tests, according to a report in German newspaper Bild am Sonntag.

During tests conducted by Germany’s Federal Motor Transport Authority (KBA) in the wake of the VW dieselgate crisis, authorities are reported to have discovered that some Fiat vehicles were only running their pollution reducing systems for just 22 minutes. An official laboratory emissions test runs for about 20 minutes.

Reports suggest that it was test on a Fiat 500X that exposed the issue. A spokesman for Fiat declined to comment.

The paper also alleged Bosch had informed German investigators that Fiat was using a system that either stopped or greatly reduced the effectiveness of emissions-reducing filters. Bosch declined to comment.

While the German authorities have not formally commented on the nature of the Fiat investigation, German transport minister Alexander Dobrindt did single out Fiat while announcing the results of tests on numerous diesel-powered cars last Friday, saying, "We will need to carry out further tests on Fiat models".

As a result of the wider tests, Dobrindt led demands for 17 manufacturers to voluntarily recall cars that emitted “excessive” amounts of NOx in real-world testing. While all of the cars meet regulatory requirements, the German government wants the manufacturers to act. So far, only Audi, Mercedes, Opel, Porsche and Volkswagen have said they will. Subsequently, the British government has demanded the manufacturers make the same updates on cars sold in Britain.

Last week Mitsubishi was forced to admit it had cheated in four fuel economy tests in Japan, and later admitted the issue may be more widespread, Peugeot's offices were raided by investigations looking into the emissions scandal, and Mercedes launched an investigation into its emissions strategy on vehicles sold in the US.