Gareth Bale has been reported by LaLiga to the Spanish Football Federation over his celebration in Real Madrid's 3-1 derby win at Atletico Madrid on Saturday.
After scoring his side's third goal in the 74th minute, the Real forward waved his right hand by his head before lowering the arm and then, as he began to raise it again, bringing his left hand down into the middle of it.
A statement on LaLiga's official website said: "In minute 73 of the game, after Gareth Bale, number 11 of Real Madrid, scored his team's third goal, some jeering is heard from the home crowd by the audio-visual recordings during the celebration.
"And he moves his right arm up towards his head in a signal of provocation towards the fans, creating a possibly obscene gesture by moving his other arm and striking halfway up his right arm."
The statement included reference to a possible suspension of four to 12 games.
The goal was the 29-year-old Wales international's 100th for Real, who he joined from Tottenham in 2013.