A clash between fans before a Brazilian league match left about 30 people injured and 158 were detained.
Authorities said fans used bricks, stones and pieces of wood in the brief confrontation before the scoreless draw between Palmeiras and defending champion Sao Paulo at Palestra Italia stadium on Sunday.
Police officer Adelino Sobrinho told the Web site of the Folha de S. Paulo newspaper that about 400 fans participated in the violence, which was organized by fans from both teams in online communities.
All injuries were minor, and most of those detained were released after brief interrogations.
Two police officers were injured after being hit by stones thrown at them during the confrontation.