"An investigation is underway, targeting unidentified people from the former PSA group," a spokeswoman for the Frankfurt prosecution told AFP.
"The investigation is linked to engines used in SUV cars" of these three brands, she added, without further details.
The sprawling "dieselgate" scandal erupted in 2015, when Volkswagen admitted to tampering with 11 million of its diesel cars to hide the true level of their most toxic emissions.
The revelations by US environmental officials quickly turned into a big deal of fraud that swept through the auto industry.
Several manufacturers and equipment suppliers have since been in the sights of justice beyond the borders of Germany, where the first lawsuits against former officials of the Volkswagen group are underway.
In France, judicial inquiries were opened in Paris from 2016. Peugeot and Citroën were indicted there in June, along with Renault and Fiat Chrysler, by judges from the public health department of the Paris court.
The French Repression of Fraud (DGCCRF) mentioned in a report in 2017 a "global strategy to manufacture fraudulent engines, then to market them".
In Germany, searches notably targeted Mitsubishi in 2020, which this year paid a fine of 25 million euros and claims to have committed "no fraud".
The case has already cost more than 30 billion euros to Volkswagen, largely in the United States where the German group pleaded guilty to fraud in 2017.
© 2021 AFP