Updated

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.