Real Madrid coach Xabi Alonso said his defender Antonio Rudiger had complained of a racist incident at the end of Sunday's 3-1 Club World Cup win over Mexican side Pachuca.
Rudiger was visibly angered following an exchange of words with Pachuca's Gustavo Cabral after the final whistle and spoke to Brazilian referee Ramon Abatti Abel.
Cabral denied he had racially abused the German centre-back.
Asked about the incident in the post-match press conference, Alonso said: "Toni told us something, we support Toni and we will see what happens.
"I think the FIFA protocol has been activated to investigate, but if it has happened, all measures should be taken and we support Antonio because it's something unacceptable.
"In football there is no tolerance for this, and if it happened, then measures should be taken. This is what Antonio has told us and we believe him. It's being investigated now," he said.
Cabral, 39, spoke after the game and said his words had been misinterpreted by Rudiger.
The Argentine said he had called the defender a "coward", with the Spanish phrase he used similar to another which is linked to racist abuse.
"The referee made the racism sign but I was telling him the same thing the whole time – (coward)," said Cabral.
Pachuca coach Jaime Lozano was also asked about the incident but said he was unaware of what had happened.
"I just found out from you, you are letting me know, we did not talk about it in the dressing room, I haven't spoken to Cabral about this, I cannot give you an explanation about it because this is the first (I have heard of) this news," he said.
"It cannot be justified at all but I will talk to him, I've known him for a little while and and I have never heard of something like that with Pachuca players. I cannot defend my captain at any cost but I will talk about it with him," he said.
FIFA did not immediately respond to a request for comment.