Volkswagen will start firing people responsible for rigging US emissions tests and shake up management, two sources familiar with the plans said, as the German carmaker tries to get to grips with the biggest scandal in its 78-year history.

The supervisory board of Europe’s biggest automaker is meeting today to decide a successor to chief executive Martin Winterkorn, who resigned on Wednesday.

The sources said it would give initial findings from an internal investigation into who was responsible for programming some diesel cars to detect when they were being tested and alter the running of the engines to conceal their true emissions.

Top managers could also be replaced, even if they did not know about the deception, with US chief Michael Horn and group sales chief Christian Klingler seen as potentially vulnerable.

Volkswagen shares have plunged around 20 per cent since US regulators said the company could face up to $18 billion in penalties for falsifying emissions tests.

The company said on Tuesday 11 million of its cars globally were fitted with engines that had shown a “noticeable deviation” in emission levels between testing and road use.

Regulators in Europe and Asia have said they will also investigate, while Volkswagen faces criminal inquiries and lawsuits from cheated customers.

When he resigned, Winterkorn denied he knew of any wrongdoing but said the company needed a fresh start.

“There will be further personnel consequences in the next days and we are calling for those consequences,” Volkswagen board member Olaf Lies told the Bavarian broadcasting network, without elaborating.

The heads of Volkswagen’s Porsche brand, Matthias Mueller; Audi brand, Rupert Stadler; and VW brand, Herbert Diess, are seen as the front-runners to succeed Winterkorn, three people familiar with the matter told Reuters on Wednesday.