Spanish police have stopped Maxi Mazzaro, one of the leaders of Boca Junior ultras (known as the Barras Bravas in South America), at Madrid’s Barajas airport and deported him back to Argentina.

According to police sources of Spanish news agency EFE, Mazzaro was detected by authorities and not allowed to enter Spain as part of security measures ahead of the Copa Libertadores final between Boca Juniors and River, which will be held at Real Madrid’s Santiago Bernabéu stadium on Sunday.

Mazzaro was stopped on Wednesday night and has already returned to Argentina, according to EFE sources. Mazzaro has an extensive criminal record and Spanish police consider him to be one of the most “important and dangerous” members of the Boca Ultras.

Spanish authorities are taking extensive precautionary measures for Sunday’s final to avoid any repeat of the pre-match violence in Buenos Aires that led to the game being cancelled on two occasions and subsequently moved to the Spanish capital.

The controversial decision to move the final out of South America to Europe has been heavily criticized by both clubs, its fans and by many South Americans in the footballing world. But despite the backlash to the Conmebol decision, the game will go ahead at the Bernabéu on Sunday at the local time of 20:30.