Real fans reported for fascist behaviour
Referee Alfonso Perez Burrull said in his report that some Real fans in an area behind one of the goals were waving flags and banners with "extremist or radical symbolism".
He also referred in the report to "chants making reference to the gas chamber, death to Osasuna and fascists forever" and said they were accompanied by gestures and signs "of a fascist nature".
Real, who came back from a goal down to win the match 3-1, have had trouble in the past with a group of radical fans known as the "Ultra Sur".
The club were fined 9,780 euros ($13,010) after television pictures showed members of the group insulting visiting black players and making Nazi salutes in a Champions League match against Bayer Leverkusen in 2004.
The club will likely face another fine from the Spanish soccer federation (RFEF) following Sunday's incidents.