BERLIN (Reuters) - Volkswagen (>> Volkswagen) will hold an extraordinary supervisory board meeting to discuss allegations about a cartel in the auto industry, a source familiar with the matter said on Monday.

A VW spokesman confirmed that an extraordinary supervisory board meeting would be held on Wednesday but declined to give further details.

German magazine Der Spiegel said German carmakers Daimler (>> Daimler), VW, BMW (>> Bayerische Motoren Werke) and Porsche held discussions about how to calibrate the size of tanks containing AdBlue, a urea-based liquid needed to help filter nitrogen oxides from diesel emissions.

(Reporting by Andreas Cremer; Writing by Edward Taylor; Editing by Maria Sheahan)

Stocks treated in this article : Bayerische Motoren Werke, Daimler, Volkswagen