Cape Town - A Brazilian radio reporter was felled by a rocket thrown onto the pitch during Sunday's Cruzeiro-Atletico Mineiro derby in Belo Horizonte, Sportv reported.
The reporter was not hit directly but was knocked to the ground and treated by doctors. He was not badly injured and was later released, Sportv and the Globo media web site said.
A Cruzeiro fan was arrested by police in the Mineirao stadium. Police could not be reached for confirmation.
Flares and rockets are not allowed into stadiums in Brazil but organised fans groups are able to sneak them past police searches at the turnstiles. In 2013 a young Bolivian fan was killed by a flare fired by Corinthians supporters in a Libertadores Cup game.
Sunday's match ended 1-1 and was watched by 35 390 people, the highest crowd on a day when local derbies were played all across Brazil.
Rafael Carioca got the opener for Atletico after 71 minutes but Leandro Damiao equalised 11 minutes later with his fifth goal in nine games since signing for the club at the start of the season.
Many of the other fixtures were watched by disappointing crowds. In Sao Paulo, a metropolitan area of more than 20 million people, only 18,000 people turned out to see Sao Paulo lose 1-0 at home to Corinthians.
Danilo got the winner after 11 minutes, with Sao Paulo goalkeeper Rogerio Ceni missing a penalty.
In Rio, Fluminense handed Botafogo their first defeat of the season with a convincing 3-1 win at the Maracana. Less than 22,000 people paid to watch the game, while in Goias state, less than 2,000 people watched Goias beat Atletico-GO 1-0.