Volkswagen is set to appoint Matthias Muller, the chief executive of Porsche, as its new leader amid a widening scandal over its gaming of emissions testing affecting 11 million of its diesel vehicles, according to several reports.

Muller is expected to be named to the post on Sept. 25 following an executive board meeting, reports Reuters. He would replace Martin Winterkorn, who resigned on Sept. 23.

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 models, such as the Jetta TDI, Beetle TDI, Golf TDI, and Audi A3 TDI. The Passat TDI is affected from the 2014-MY and 2015-MY.

The company could face a fine of up to $18 billion, according to the U.S. Environmental Protection Agency.