Four Real Madrid players including Kylian Mbappé and Vinícius Júnior are being investigated for alleged “indecent conduct” during the Champions League game at Atletico Madrid, UEFA said on Thursday.

UEFA said it appointed a disciplinary inspector to study the unspecified allegations at the round of 16 game on March 12. The case also involves Antonio Rüdiger and Dani Ceballos.

Video clips circulating on social media showed Mbappé grabbing his crotch during celebrations on the field for Madrid winning a penalty shootout.

Any ban imposed would force a player to miss Madrid’s game at Arsenal on April 8 in the first leg of the quarterfinals.

Madrid advanced to the quarterfinals after the shootout against Atletico. Rüdiger scored the decisive spot kick and led teammates in an exuberant dancing run around Atletico’s home field.

In a similar case prosecuted by UEFA at the European Championship last year, Madrid player Jude Bellingham was given a one-game ban suspended for a probationary period of one year.

Bellingham scored a stoppage-time goal for England to level a round of 16 game against Slovakia when he gestured his hand toward his crotch. England went on to win 2-1 in extra time.

UEFA disciplinary judges found Bellingham guilty of “violating the basic rules of decent conduct” and fined him 30,000 euros ($32,400).