LONDON, May 31 (Reuters) - Mercedes and Ferrari have been asked to reply to a disciplinary enquiry into tyre tests they carried out with Pirelli this season, Formula One's governing body said on Friday.
The International Automobile Federation (FIA) said in a statement the enquiry was "in pursuance of the FIA Judicial and Disciplinary rules" and followed a stewards' report submitted after last weekend's Monaco Grand Prix.
A spokesman for the governing body said the two teams had been asked to reply to a list of questions and had not yet been summoned to any formal hearing.
Ferrari and champions Red Bull submitted protests in Monaco after discovering Mercedes carried out a test for Pirelli with their current car in Spain this month in an apparent breach of a testing ban during the season.
It has subsequently emerged from media reports that Ferrari also tested, albeit with an older car, for Pirelli earlier in the season. (Reporting by Alan Baldwin, editing by Tony Jimenez)