Volkswagen has appointed Matthias Muller, the chairman of Porsche AG, as its new chief executive to replace the departed Martin Winterkorn, and will restructure its North American operations in the wake of a scandal over diesel emissions.

Muller, 62, will serve as an interim chief executive until Volkswagen can find a successor, the company has announced.

Volkswagen is also realigning its North American operations by combining markets of the U.S., Canada, and Mexico under a new region that will be led by Winifried Vahland, who leads the company's Skoda division.

Michael Horn will remain president and chief executive of Volkswagen Group of America. Horn, who began his role in January of 2014, gained the support of Volkswagen dealers, who released a statement Sept. 24 lobbying the automaker to retain him.

With Vahland's promotion, which includes a seat on the Board of Management, Volkswagen has named Bernhard Maier to lead its Skoda automotive unit based in the Czech Republic. Maier takes the title of chairman of the Skoda board of directors.

In a related move, Volkswagen will create a Porsche brand group that will now include Bentley and Bugatti. The Audi brand group will continue with Lamborghini and Ducati. Spanish automaker SEAT will also retain a board position, along with the Truck Holding, Power Engineering, and Financial Services business units.

Christian Klingler, Volkswagen AG's board member in charge of sales and marketing, is leaving the board in a move not related to the scandal. Jürgen Stackmann, chairman of SEAT, will take over Klingler's role. Stackmann is succeeded by Luca de Meo, Audi AG Board of Management member for sales and marketing. These personnel changes become effective from Oct. 1.

On Sept. 18, the EPA accused Audi and Volkswagen of using a software algorithm in its four-cylinder diesels to circumvent federal emissions standards. The cars from the 2009 to 2015 model years could detect when the car is undergoing official emissions testing and turn on full emissions controls only during that test. This would violate the Clean Air Act.

The allegations cover about 11 million models ranging from the 2009 to 2015 model years, such as the Jetta TDI (2009-2015), Jetta SportWagen (2009-2014), Beetle TDI (2012-2015), Golf TDI (2010-2015), Golf SportWagen (2015), Passat TDI (2012-2015) and Audi A3 TDI (2010-2015).