Germany's motor vehicle authority - the KBA - is investigating Porsche over the suspected manipulation of petrol engines to achieve improved emissions data.
A KBA spokesman said Monday (August 24) the investigation involved petrol engines that Porsche produced for the European market before 2017.
The Volkswagen-owned brand had confirmed a newspaper report on Sunday (August 23) that it had informed the authorities after internal investigations uncovered suspected irregularities.
German prosecutors fined Porsche $632 million last year for lapses that allowed the company to cheat diesel emissions tests, but manipulation has not yet been proven for petrol engines.
A Porsche spokesman on Sunday said the issues relate to vehicles developed several years ago, adding there were no indications that current production was affected.
He also said that the carmaker is working closely with authorities.