Volkswagen's pollution cheating program was developed by dozens of managers, not just a handful of individuals as the company has suggested, news site Spiegel Online reported on Wednesday.

The German auto giant last month caused global outrage when it admitted that it fitted 11 million diesel vehicles with software designed to evade pollution tests.

Preliminary results of investigations carried out by VW and a US law firm suggest that "the emissions fraud was not only created by a small group of managers, as the company claims", said Spiegel Online without citing its source.