Update, 9/25: Porsche CEO Matthias Müller has been named the new CEO of Volkswagen Group by the company's Supervisory Board. In a statement, Müller wrote, "My most urgent task is to win back trust for the Volkswagen Group—by leaving no stone unturned and with maximum transparency, as well as drawing the right conclusions from the current situation. Under my leadership, Volkswagen will do everything it can to develop and implement the most stringent compliance and governance standards in our industry."

Update, 9/24: The Wall Street Journal reports that a source close to the matter has re-affirmed that Porsche CEO Matthais Müller will take over as head of Volkswagen Group. Rumors of Winterkorn's resignation and Müller's succession were reported on Monday, but Volkswagen denied the reports. Our original report on Winterkorn's resignation is below.

Martin Winterkorn, the CEO of Volkswagen Group, resigned today amid a scandal involving the emissions control systems on Volkswagen and Audi diesel vehicles. According to Bloomberg, he could benefit from a $32 million pension on his way out. If the company's supervisory board decides he is not responsible for the circumstances surrounding his exit, Winterkorn could also reap millions more in severance.

In his notice of resignation, published on Volkswagen’s website, Winterkorn wrote, "I am shocked by the events of the past few days. Above all, I am stunned that misconduct on such a scale was possible in the Volkswagen Group."

The Volkswagen Group owns automotive brands such as Volkswagen, Audi, Porsche, Bentley, Lamborghini, and others. Last week, the US Environmental Protection Agency (EPA) issued a Notice of Violation to the company, saying that a variety of Volkswagen and Audi vehicles made after 2009 were shown to have “defeat devices” on them. The software on a defeat device reduces the efficacy of a car’s emissions control system while it operates under normal conditions, but it allows the emissions control system to operate normally while the car is being tested for emissions compliance. That way, Volkswagen could allegedly offer cars with better performance while ignoring federally mandated emissions regulations in the US.

At first, the EPA cited about 500,000 vehicles in the US that were affected by the device. After Winterkorn publicly apologized for the scandal over the weekend, Volkswagen released a statement saying that nearly 11 million vehicles worldwide had the deceptive software on them. Rumors suggested that Winterkorn would be ousted and replaced by Porsche’s CEO, but Volkswagen denied the information.

In his resignation notice today, Winterkorn wrote, "As CEO I accept responsibility for the irregularities that have been found in diesel engines and have therefore requested the Supervisory Board to agree on terminating my function as CEO of the Volkswagen Group. I am doing this in the interests of the company even though I am not aware of any wrong doing on my part.”

In the US, Volkswagen could face up to $18 billion in fines, and executives like Winterkorn could face criminal prosecution.

"Volkswagen needs a fresh start—also in terms of personnel,” Winterkorn continued. "I am clearing the way for this fresh start with my resignation."

In a statement to Ars, a Volkswagen spokesperson said Winterkorn's successor has not been decided yet. The new CEO—very likely Matthais Müller, according to the WSJ report—will be decided at Volkswagen's Friday supervisory board meeting.