Power utility Eskom on Wednesday called on consumers to switch off geysers, pool pumps and all non-e.
World Cup organisers said yesterday that about 100 seats were destroyed at the Arena Castelao by Fortaleza fans upset that the team missed out on promotion.
The stadium will host six matches in next year's World Cup. Local media, citing police, said the number of damaged seats could be close to 3000.
Police also confronted fan groups inside two other stadiums, including where Brazilian league leaders Cruzeiro played on Sunday.
Several teams have been punished by Brazil's sports tribunal this year because of fan violence, and more penalties are expected after this weekend.
No serious injuries were reported in the incidents.