German authorities have found what they consider an illegal "defeat device" in a Porsche diesel model that manipulates emissions levels, leading to the recall of some 22,000 cars.
The model affected is a Cayenne 3-litre TDI that is still in production, transport minister Alexander Dobrindt said on Thursday.
Authorities will order an obligatory recall as in previous such cases, he added, saying 7,500 of the vehicles have been registered in Germany and 22,000 across Europe.
It is not clear how many more are with dealers or in production.
Mr Dobrindt said the finding resulted from tests carried out by German authorities.
He said "a so-called warm-up strategy" is triggered when cars are being tested that is not activated during normal driving. The emissions of nitrogen oxide, a pollutant that is harmful to health, are much higher when the car is on the road, he said.
Talks with the manufacturer also raised suspicions there may be similar software in a Volkswagen Touareg 3-litre diesel model, but authorities still have to carry out tests on it, Mr Dobrindt added.
Speaking about the Cayenne, he said: "There is no explanation as to why this software is in this car," arguing that the vehicle has a modern emissions system and is technically able to comply with emissions limits. That should mean Porsche can quickly produce modified software that complies with the law, he added.
Porsche is a unit of Volkswagen, which has been under a cloud since 2015 over its equipping of diesel cars with illegal software that enabled cheating on emissions tests.
Volkswagen has agreed to billions of pounds in fines and civil settlements over that scandal.