Volkswagen AG announced Thursday it is expanding the scope of its internal investigation manipulation of emissions to determine whether additional models of its diesel engines possessed trick software.

The automaker admitted last month to manipulating emission tests on some diesel-powered cars and light commercial vehicles in the U.S. and Europe equipped with the EA 189 engine built to the "Euro 5" emissions standard, reported The New York Times. VW is under investigation on suspicion of fraud in both countries and is preparing to launch a recall of up to 11 million vehicles.

VW spokesman Pietro Zollino said Thursday that the company is now checking whether models with the EA 288 motor built to the same emissions standard has the same software, reported the Associated Press. He failed to say how many cars are being checked, however.

He also mentioned that none of the vehicles built to the "Euro 6" standard contain the cheating device, saying they all meet legal standards, according to the Wall Street Journal.

The internal investigation is still in its early stages, and thus far only five high-ranking executives have been suspended for their connection to the scandal. One of the main goals of the investigation is to determine how many people were in the know about the cheating, and it's expected that at the investigation's end, more than the five executives will be implicated for their involvement in the plot.