The automaker is investigating whether the diesel motor line known as EA 288, which is used on popular VW vehicles like the Golf, also included a “defeat device” that allowed it change its pollution emissions during tests with regulators.

Another VW engine called EA 189 is the one that has already been reported by the EPA and is equipped in more than 11 million vehicles. The EA 288 itself may also be in millions of cars, according to the New York Times.

The investigation could lead to even more financial and reputational damage for Volkswagen, which is already planning to recall 8.5 million vehicles in Europe and about half a million in the United States. New CEO Matthias Muller recently said the company’s costs related to the scandal may exceed the $7.4 billion it has already set aside for recalls.

So far VW has suspended five executives for their roles in the cheating scandal, and CEO Martin Winterkorn also resigned.