German prosecutors have widened their investigation of Volkswagen to include suspicions of tax evasion linked to the emissions cheating scandal.

Prosecutor Birgit Seel said the probe was focused on five Volkswagen employees but did not release their names.

The focus of the investigation is on tax breaks Volkswagen received for producing low-polluting cars that it might not have qualified for if the emissions had been correctly reported, Ms Seel said.

Volkswagen has acknowledged it produced 11 million vehicles worldwide with small diesel engines that contained software allowing them to cheat nitrogen oxide tests.

Earlier this month, the car maker also said it found "unexplained inconsistencies" in carbon dioxide emissions from more of its vehicles.

Chief executive Matthias Mueller told company managers that all technical details on how to fix cars fitted with emissions rigging software in Europe would be provided to Germany's Federal Motor Transport Authority by the end of November, and that most would not require major work.

He said the agency has already signed off on a software update which will be enough to fix affected two-litre diesel motors, and has given the "basic go" to a fix for the 1.6-litre vehicles that will involve a software update and a "relatively simple" replacement of an air filter cartridge and grill.

Details are still being finalised on a fix for 1.2-litre motors, but it should also just require a software update.

Mr Mueller said: "For about 90% of the group's vehicles in Europe the solutions are now confirmed.

"The cost for the retrofitting is technically, physically and financially manageable. That is a good development."

Meanwhile, Volkswagen subsidiary Audi said it had agreed to revise and resubmit to US authorities the parameters of its engine-management software used in the V6 TDI three-litre engine, which is used in its American models A6, A7, A8, Q5 and Q7 from 2009 on.

Volkswagen also uses the engine in the Touraeg, and Porsche has used it in the Cayenne since 2013.

Once approved by the Environmental Protection Agency and the California Air Resources Board, it will be installed in the affected vehicles.

The company acknowledges that so-called "auxiliary emissions control devices" - the software used to help the cars pass the tests - were "not sufficiently described and declared" for US approval, and that one "is regarded as a defeat device according to applicable US law".

Audi estimated the costs of the fix to be in the "mid-double-digit millions".