German auto giant Volkswagen said Tuesday an internal probe in the wake of its pollution cheating revelations had found that 800,000 more vehicles showed "inconsistencies" related to carbon emissions.

"During the course of internal investigations, unexplained inconsistencies were found when determining Type Approval CO2 levels. Based on present knowledge around 800,000 vehicles from the Volkswagen Group are affected," the company said in a statement.

"An initial estimate puts the economic risks at approximately two billion euros," it added.