UEFA has announced it is to open an inquiry into Real Madrid's claim that Barcelona midfielder Sergio Busquets racially abused Marcelo.
Madrid released footage on their in-house TV channel of Busquets shouting in the direction of Marcelo during Barcelona's 2-0 Champions League victory at the Bernabeu last month. Busquets was captioned as saying "mono, mono" ("monkey, monkey").
A UEFA statement read: "UEFA has opened disciplinary proceedings against FC Barcelona midfielder Sergio Busquets, who is alleged to have violated Article 11 bis of the UEFA Disciplinary Regulations by directing racist abuse towards a Real Madrid CF player in the UEFA Champions League semi-final first leg between the clubs on 27 April.
"The proceedings have been launched on the basis of evidence provided by Real Madrid (video and statement of club and player). The UEFA Control and Disciplinary Body will deal with the case on Sunday 15 May and the decision will be communicated to the club on Monday 16 May."
UEFA's Disciplinary Regulations state that any person found guilty of the offence could be suspended for up to five matches.
Article 11 bis states: "1. Anyone who insults the human dignity of a person or group of persons, by whatever means, including on grounds of colour, race, religion or ethnic origin, shall incur a suspension for five matches or for a specified period.
"2. Any member association or club whose supporters engage in the behaviour described in paragraph 1 shall incur a minimum fine of €20,000.
"3. If particular circumstances so require, the disciplinary body may impose additional sanctions on the member association or club responsible, such as the playing of one or more matches behind closed doors, a stadium closure, awarding of a match by default, deduction of points or disqualification from the competition.
"4. Any form of extremist ideological propaganda is banned before, during and after matches. The sanctions laid down in paragraphs 1 to 3 above apply."