Some sitting sections started being removed on Tuesday, kick-starting work to make the famed venue ready for football's biggest showcase in four years.
The stadium, which is expected to host the World Cup final, will not be immediately closed, but its capacity will be reduced during the renovation.
More than 80,000 fans packed the Maracana in a Brazilian league match between Fluminense and Vasco on Sunday.
The stadium, built for the 1950 World Cup., will likely be used in the 2013 Confederations Cup.
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