Audi said Monday it will spend about 50 million euros upgrading software that regulators believe flouts US pollution limits in larger diesel cars in the US.

The upscale brand of embattled German auto giant Volkswagen said the repairs will cover auxiliary emission control devices (AECD) for V6 diesel 3.0-liter cars that the Environmental Protection Agency has since early November alleged violate US emissions laws.

Audi "estimates that the related expense will be in the mid-double-digit millions of euros," the company said in a news release.

EPA said Friday that Audi had told US regulators that three-liter diesel models since 2009 contain the AECD.

The US agency alleges that the AECD permitted Audi to evade US emissions controls.

Audi maintains that the system was not devised to evade the emissions limits, but to redirect gases in order to reduce emissions of carbon dioxide.

However, Audi has admitted that it did not disclose the AECDs as required under US law.

The models affected are the A6, A7, A8, Q5 and Q7. The problem affects about 85,000 Audi, Porsche and Volkswagen vehicles in the United States.

Allegations about the three-liter cars are connected to a larger scandal that has engulfed Volkswagen since September.

Volkswagen is struggling to cope with the biggest crisis of its history over its admission in September that it had fitted more than 11 million vehicles worldwide with devices designed to cheat pollution tests.