BERLIN (AFP) - Volkswagen's pollution cheating programme 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 cheat 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.

"Dozens of Volkswagen managers were implicated, insiders speak of at least 30 people," said the report, adding that "they are to be suspended".

A Volkswagen spokesman, however, rejected the claim, saying "the number is without foundation".

The group has promised to shed light on how the cheating could have happened, but top managers have already pointed the finger at a handful of people, and suspended several of them, without confirming their identities.

Volkswagen's new chief Matthias Mueller has said four employees had been suspended, adding however that he did not believe that top management could have been aware of the scam.

Among those suspended is the technical director of Audi, according to German media.

Meanwhile, Volkswagen's Czech brand Skoda said its former boss Winfried Vahland, who had been appointed to head the VW group's North America operations, had quit the company.

Vahland was leaving due to differences of opinion over the organisation of VW's North American operations, Skoda said, adding that the decision had nothing to do with the pollution cheating scandal.