Offices in Germany linked to Mitsubishi, including its research and development centre, have been raided as part of an investigation by the Frankfurt prosecutor’s office.
The prosecutor's office says it is investigating whether Mitsubishi vehicles fitted with the company's 1.6- and 2.2-litre four-cylinder turbocharged diesel engines used illegal software to pass emissions tests.
In a statement to Reuters, Mitsubishi Motors Europe said it "will of course collaborate and contribute to this investigation", and confirmed locations associated with the company had been searched.
Supplier Continental also said it is aiding investigators.
A spokesperson for Mitsubishi Motors Australia has told CarAdvice: "Mitsubishi Motors was informed of an inspection this morning of its German Distributor as well as of its European R&D facilities, also based in Germany, by European authorities.
"We are awaiting clarification from Mitsubishi Motors Corporation in Japan as to whether this investigation impacts any vehicles outside of Europe."
Interest in the emissions of diesel vehicles in real-world conditions increased in 2015 when the Volkswagen Group admitted it had been using defeat devices to illegally allow some of its diesel engine families to pass US certification.
These defeat devices were able to detect when the car was being tested in laboratory conditions. In these circumstances the software would ensure the vehicle's emissions of oxides of nitrogen (NOx) gases were within legal limits.
In real-world driving, though, most of these pollution control systems would be turned off or dialled down to improve performance, increasing NOx output well beyond legal levels.
Since the Dieselgate scandal came out into the open, numerous investigations and court actions have been launched on both sides of the Atlantic.
In September 2019, Daimler, owner of the Mercedes-Benz marque, agreed to pay a €870 million ($1.4 billion) in Germany for non-compliance with diesel emissions regulations, while Fiat Chrysler settled with US authorities for US$800 million ($1.2 billion) in June.
Locally, Volkswagen was fined $125 million late last year by the Federal Court for making "false representations" about the emissions of over 57,000 diesel vehicles.