SAO PAULO -- SAO PAULO (AP) — Seats were destroyed at a World Cup stadium in Fortaleza last weekend and dozens of supporters detained after clashes in Sao Paulo.

World Cup organizers said Monday that about 100 seats were destroyed at the Arena Castelao by Fortaleza fans upset with the team missing out on promotion to the second division. The stadium is to host six matches in next year's World Cup.

Local media, citing police, said the number of damaged seats could be close to 3,000.

Police also confronted fan groups inside two other stadiums, including the site of a match Sunday involving Brazilian league leader Cruzeiro.

No serious injuries were reported in the incidents.

Several teams have been punished by Brazil's sports tribunal this year because of fan violence, and more penalties are expected. Vasco da Gama, Corinthians and second-division club Palmeiras all have lost home games because of fan confrontations this year.

Two weeks ago, the first-division match between Atletico Paranaense and Botafogo in the World Cup host city Curitiba was delayed at halftime because of fan fighting in the stands. That same weekend, a second-division game in the host city of Natal was delayed for nearly an hour because fans jumped onto the field to escape overcrowded stands.

The problem at the Arena Castelao occurred after third-division club Fortaleza couldn't manage more than a 2-2 draw against Sampaio Correa, a result that kept the traditional northeastern club from having a chance to reach the second division. Nearly 60,000 Fortaleza fans packed the stadium, and some of them began destroying the seats after the final whistle. The goal that sealed Fortaleza's elimination came in second-half injury time.

Local World Cup organizers told The Associated Press they were still assessing the damage at the venue, but an initial probe showed that about 100 seats and some portable toilets will have to be replaced.

Brazil will play one of its group-stage matches at the Arena Castelao, which was the first World Cup stadium for next year's tournament that has been completed.

At the Morumbi Stadium, police hit fans with batons to keep Sao Paulo supporters from invading the Corinthians fan section. Television images showed bloodied fans throwing punches at officers and some fans with small children trying to flee the chaos.

After the match, supporters from both teams clashed at a major avenue. A bus carrying Sao Paulo fans had nearly all of its windows destroyed and police seized several iron bars and rocks used in the confrontation.

Authorities detained at least 30 people involved in the clash, including several women. The Lance sports daily showed a video of dozens of Sao Paulo supporters lying on the ground face first and with their hands on their heads.

At the Independencia Stadium in Belo Horizonte, police had to use tear gas to contain Cruzeiro fans during the team's 1-0 loss to rival Atletico Mineiro. Police found homemade bombs with some of the fans, and television images showed that at least one of the devices was hurdled into the seating section where Atletico Mineiro were staying. No one was reportedly injured.

A few dozen fans were detained before the match as rival groups clashed outside the stadium, according to local media.

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