FRANKFURT -- A German government committee has asked for further tests on 30 cars it says have "inexplicably high" CO2 emissions.
Germany initially tested the diesel cars for defeat-device software after Volkswagen Group admitted to manipulating engine management software to cheat tests for the health-harming NOx pollutants.
But officials were surprised that many of the cars showed high levels of emissions of CO2, a gas blamed for climate change.
"Out of 53 cars tested for illegal software, 30 were showing inexplicably high CO2 emissions. The experts are now looking into this," a spokeswoman from the German transport ministry told Automotive News Europe.
The ministry did not say which cars will be retested and which brands they came from. The KBA motor transport authority said in November that it was testing cars from major automakers including VW Group brands, Ford, Opel, BMW, Mercedes-Benz, Fiat, Renault, Peugeot and Toyota.
The committee will present a CO2 report following the results of these tests, the spokeswoman said.
Last week Opel and Fiat were asked to appear before a German government commission to explain high NOx emissions from diesel versions of the Opel Zafira minivan and Fiat 500X. Fiat was criticized for not attending the meeting.
The KBA has found that only VW Group used a defeat device but it is investigating techniques used by automakers to tweak engine performance in a way that results in high emission levels outside test conditions.
Reuters contributed to this report.