Volkswagen CEO Matthias Müller said Monday that the steps required to fix millions of its vehicles in Europe that are equipped with software to cheat on emissions tests are “manageable.”

Müller reportedly said that Germany's Federal Motor Transport Authority has signed off on a software update to fix vehicles carrying the affected 2-liter diesel motors. Of the over 11 million VW vehicles programmed to cheat on emissions tests, the majority are in Europe, while about 500,000 are in the United States.

"The efforts (needed) to carry out the refits are technically, mechanically and financially manageable," Müller said, in a speech to managers at the company's Wolfsburg base Monday, according to Reuters. "This is a good development."

Müller also said Monday that the inquiry into the emissions scandal may take several months. According to reports, this indicated that the company’s internal investigation is moving slowly.

“We are speaking here of very complex occurrences, which in some cases are far in the past,” Müller said, according to the New York Times. “It will take several months before there are conclusive findings.”

In September, Volkswagen admitted it had rigged some of its vehicles with software, a so-called defeat device, that would allow the vehicles to lower their emissions levels during testing. The German automaker has set aside over $7 billion to help cover the costs of the diesel recalls.

Last week, representatives of Volkswagen and its Audi division met with officials from the U.S. Environmental Protection Agency (EPA) to present proposals for making cars in the U.S. compliant with clean air rules. Volkswagen has also been working toward new sales initiatives to rebuild trust in the U.S.

Earlier this month, the EPA said that Volkswagen had installed the cheating software on 2014 to 2016 models with 3.0 liter, six-cylinder diesel engines, which included Audi and Porsche models.