Two people were taken into custody after allegedly invading a team dressing room and attacking a player before the start of a Brazilian state league game between Flamengo and Macae on Saturday.
Members of an unidentified Flamengo fan group allegedly stole belongings, cleats and fruit from the Macae club's dressing room and assaulted goalkeeper Ricardo Berna, who played Saturday's game with a bandage on his chin, the director of competitions for Rio de Janeiro's football federation, Marcelo Vianna, told Globo.com.
"I'm sorry for this wild attitude of a small group of supporters. It was just a cut on the goalkeeper, but it could have been much worse," Vianna said.
Police said a group of 10 people entered through an unattended gate at the Estadio Claudio Moacyr de Azevedo in Rio de Janeiro, then fled.
"There was an entrance gate that is not of the police's responsibility, that should have been closed from the inside, but was not. When a group of fans saw that the gate was unlocked, they accessed the stadium," captain Ricardo dos Santos said.
"The police on duty nearby, when they saw, intervened. The group ran, and it was not possible to make identifications. ... It was a big rush of not more than 10 fans."
When speaking to reporters before the game, Berna estimated the number of invaders to be about 100.
Flamengo president Eduardo Bandeira de Mello said he was unaware of the incident and called the happenings "very weird."
Saturday's events come just days after Flamengo and eternal rivals Fluminense, two of Rio's biggest clubs, issued a letter informing Rio federation president Rubens Lopes they would be playing the 2015 state competition under protest, citing, among other qualms, a "dictatorial attitude" by the governing body, and would explore starting a new state competition for the following year.
Flamengo, who boast of having the largest fan base in Brazil, were subject to similar headlines midway through the 2014 season, when fans became aggressive with former Arsenal left-back Andre Santos -- then a Flamengo player -- in the aftermath of the club's 4-0 loss to Internacional in Porto Alegre.
Saturday's game finished without further incident, and ended in a 1-1 draw.