Volkswagen has admitted rigging emissions tests in Europe in the same way it falsified results in the US, Germany's transport minister has said.
Alexander Dobrindt said it was not known how many of the 11 million vehicles affected were in Europe.
He also said other manufacturers' vehicles would be checked.
The scandal began unfolding on Friday when the German car giant said it had used software in the US to provide false emission test results.
Mr Dobrindt said he had been told vehicles with 1.6 and 2.0 litre diesel engines are "affected by the manipulations that are being talked about".
The company's Jetta, Beetle, Golf and Audi A3 models in the US from 2009 to 2015, and the Passat from 2014-15, were fitted with the devices which produced doctored results. However, diesel cars are far more popular in Europe than in the US.
Analysis: Theo Leggett, Wolfsburg
The city of Wolfsburg in Lower Saxony is not merely the hometown of Volkswagen. Wolfsburg is Volkswagen, Germany's answer to Detroit - but rather more prosperous.
It was founded in the 1930s as a place to house workers building the KdF-Wagen - the car which became the VW Beetle after the Second World War.
Even today, more than half of the town's 120,000 inhabitants work at the local VW plant, a sprawling complex that covers some 6.5 sq km. Many of the rest provide the services which those employees need, such as shops and restaurants.
So a crisis at Volkswagen is a crisis for Wolfsburg.
It threatens the entire social and economic fabric of this town. People here are reluctant to speak about the scandal in the United States, wary of showing disloyalty.
But it is clear the events of the past week have taken a heavy toll.
Mr Dobrindt also said random tests would be conducted on cars made by manufacturers other than VW: "It is clear that the Federal Office for Motor Traffic will not exclusively concentrate on the VW models in question but that it will also carry out random tests on vehicles made by other carmakers."
The value of Volkswagen has shrunk by around 30% since the scandal was revealed.
Separately, BMW shares dropped by 10% on reports the false tests had been used by other carmakers.
The company issued a statement denying the report, saying the "group does not manipulate or rig any emissions tests".
"We observe the legal requirements in each country and adhere to all local testing requirements," it continued.
VW is setting aside €6.5bn (£4.7bn) to cover the costs of the scandal.
The German car giant's chief executive Martin Winterkorn resigned following the revelation.
Mr Winterkorn said he was "shocked" by recent events and was "not aware of any wrongdoing on my part".
The supervisory board said it would announce Mr Winterkorn's successor at a board meeting on Friday.
There has been speculation in German newspapers that Matthias Mueller would be named as the next chief executive. He is head of Porsche, which is part of the Volkswagen group of companies.
German public prosecutors are considering an investigation, with US authorities also said to be planning criminal investigations.