After Real Madrid defeated their city rivals on penalties to secure their spot in the quarterfinals, Antonio Rudiger, Kylian Mbappe, Vinicius Jr., and Dani Ceballos are accused of making gestures toward the home crowd.
Following the shootout triumph, TV footage showed Mbappe seemingly grasping his crotch, while German defender Rudiger appeared to make a throat-slitting move, presumably towards the audience.
According to Spanish media, Atletico told Uefa about the measures last week.
The four Real Madrid players may face suspension, but there is no assurance that the case will be heard before their quarterfinal matchup with Arsenal, which has a first leg at Emirates Stadium on April 8 and a second leg a week later. Uefa said in a statement that "[A] ethics and disciplinary inspector has been appointed to investigate allegations of indecent conduct." "Further information regarding this matter will be made available in due course."