Volkswagen and Audi executives are expected to meet U.S. environmental regulators this week ahead of a deadline to submit a plan to fix nearly 500,000 diesel cars that are equipped with the rigged emissions software, sources told Reuters Monday. The news comes as reports surfaced that the German automaker manipulated the carbon dioxide emission levels of more petrol-powered vehicles than previously disclosed.

Friedrich Eichler, Volkswagen’s powertrain development chief, is scheduled to meet with the Environmental Protection Agency (EPA) and the California Air Resources Board (CARB) later this week ahead of the Nov. 20 deadline to discuss the company's efforts to fix the vehicles that do not comply with government emissions standards, according to the sources. A separate meeting is planned between U.S. regulators and senior Audi officials.

Volkswagen has been rocked by the revelation of emissions cheating practices that came to light in September when the EPA issued a notice of violation that certain diesel engine cars made by the automaker had a programming that lowered emissions readings during testing. Volkswagen admitted it had rigged emission levels by employing a type of software, a so-called defeat device. Since then, more allegations of emissions cheating by the company have surfaced. The defeat device has affected at least 11 million Volkswagen diesel vehicles worldwide, including about 500,000 in the U.S.

Earlier this month, Volkswagen reportedly said it had understated the level of CO2 emissions in about 800,000 cars sold mainly in Europe. The company said at the time that the cheating affected mostly 1.2 and 1.4 liter diesel engines and one petrol engine, the 1.4 liter motor with a cylinder cut-off.

On Friday, Volkswagen said, in a statement, that it had also identified "implausible CO2 levels" in current petrol models such as the 1.0 liter Seat Ibiza, the 1.2 liter VW Jetta and the 2.0 liter VW Passat, according to Reuters.

In addition to the nearly half a million vehicles affected in the U.S., a whistleblower came forward shortly after the company’s new CEO, Matthias Mueller, was instated in September. That person indicated that greenhouse gas emissions were understated in as many as 800,000 vehicles in Europe, including 100,000 gas-powered cars.

Last week, Volkswagen planned to publish guidelines for whistleblowers to encourage employees to come forward with information related to the emissions scandal.