Real Madrid are being investigated by Uefa over racist chanting at the Bernabeu Stadium during a Champions League game against Bayer Leverkusen.
Fifa is also investigating racist abuse against England's black players in a friendly with Spain at the stadium.
"Fans were seen making Nazi salutes while racist chanting was directed at Leverkusen's black players," said Uefa.
The referee did not include the incidents in his report but Uefa said it would consider television evidence.
Sections of the Real support are alleged to have made monkey chants towards Leverkusen's Brazilian defender Roque Junior during the 1-1 draw.
Real Madrid issued a statement on Wednesday condemning racist behaviour but said they were unaware any incidents had taken place in the match.
The club said Uefa president Lennart Johansson, who watched the game alongside Real president Florentino Perez, had observed no problems.
England coach Sven-Goran Eriksson urged Europe's governing body to make a stand.
"Uefa have a golden opportunity to do something strong. It's a good example and I think something will happen," he said.
Speaking of the possibility of players walking off the pitch when faced by racial abuse, Eriksson said: "I never considered it during the game in Spain.
"But if that is a possibility in future I should like that. But there must be clear rules when you can do it and what happens if you do go off.
"Just say you are winning 1-0 and there was some chanting and you decided to go off the pitch, what happens? Who gets the points?
"I don't know but Fifa and Uefa can make strong rules now because of what happened in Spain."
William Gaillard, a spokesman for Uefa, said there were no set rules regarding punishment for incidents such as those seen at the Bernabeu.
"It could range from making the team play away or behind closed doors, to even the exclusion of the team," he said.
Gaillard pointed out that Roma had to play away from their stadium after violent incidents, while Slovakia were made to play one game at a different location after racist chanting against England a couple of years ago.
But he stressed: "There is no standard punishment for a particular type of offence. It depends on what is reported and previous cases."