PORTO ALEGRE, Brazil, Aug. 11 (Xinhua) -- Gremio may face the punishment of playing behind closed doors after violence broke out in the Gre-Nal derby against local rivals Internacional last Sunday.
Before the match had started a group of Gremio fans broke the barrier separating rival supporters at the renovated Estadio Beira-Rio, which was used to host games during the FIFA World Cup last month.
Gremio supporters also fought with police, leaving one injured. Gremio vs Internacional is one of the most fierce rivalries in domestic Brazilian football.
In the days before Sunday's classico the Military Brigade had held meetings with supporter groups in an attempt to quell any potential violence. But Gremio fans met outside the Estadio Olimpico - their old home - before converging on the Beira-Rio.
Prosecutors are now studying footage to try to identify those involved in the fighting. Violence also took place in the streets surrounding the stadium in the hours before the game.
Internacional won the match 2-0 and currently sit second in the Brasileirao table. The match was former Brazil coach Luiz Felipe Scolari's back in charge of Gremio.