FIFA has asked the Spanish Football Federation for information about 51 minors on the books at Real Madrid.
Under FIFA regulations minors cannot be signed from outside the EU unless the player’s parents are already moving to the club’s country.
Real Madrid rivals Barcelona were handed a 12 month transfer ban in January for signing 10 players under the age of 18, including two 12-year-old Venezuelans.
Real Madrid club director Emilio Butragueno said the club would fully comply with FIFA’s request.
“We are in agreement with FIFA on this matter, and we will continue collaborating with them in everything that is asked of us,” said Butragueno.
“We are absolutely calm about how Real Madrid has proceeded.”
On Thursday, Madrid made world headlines by signing the highly-rated 16-year-old Norwegian midfielder Martin Odegaard from Stroemgodset.