Police fired smoke bombs in a bid to stop rival football fans from fighting following championship finals across Brazil.
Seats in the 2014 World Cup stadium were ripped apart when Fortaleza supporters invaded the pitch following their side's 2-2 draw, which guaranteed them the title, against Ceara.
Fortaleza supporters used the seats, as well as sticks, to attack their rival fans, while part of the winners' stage was also ripped up in the unsavoury scenes.
"The stadium's infrastructure wasn't made for Brazilian football fans," Reuters quotes lieutenant colonel Aguinaldo as saying. "It's easy for fans to invade the field like this. Holding back a rebellious mob is difficult."
The World Cup ground in Porto Alegre was also the scene of crowd trouble, which required police intervention.
