Real Madrid and Atletico Madrid are also under investigation by FIFA for the same infractions that saw Barcelona punished on Wednesday.
Sport cites a report from AS that claims ‘reliable sources’ have said the affairs of the Madrid clubs are also being looked into by the world governing body.
Barca were banned from signing players for the next two transfer windows and given a fine regarding the signing and registering of players from outside Spain under the age of 18.
The RFEF was also fined for their role in registering the players.
Atletico and Madrid are being investigated without a complaint having been made, Sport notes.
Sport adds that Spanish football is under the microscope because the RFEF is considered an ally of UEFA rather than FIFA, and the European association and their worldwide counterparts are not on good terms.