Visiting fans are not always the problem. After the storied club River Plate lost a match in June, relegating the team to the second division for the first time in its history, its fans pulled apart their own stadium, throwing bleachers and metal poles onto the field as the police fired tear gas into the stands. Fans fought with one another and attacked reporters and the police, who used rubber bullets and water cannons to try to quell the chaos. An estimated 70 people were injured, including 35 police officers, and about 100 people were detained.

The tension was palpable at a second-division match in September between River Plate and Quilmes. Some 600 police officers set up roadblocks around the stadium to separate Quilmes and visiting River fans. After the match, Quilmes fans had to wait a half-hour for River fans to exit before being allowed to leave the stadium.

Asserting control over unruly fans is more complicated than in England, said experts who have studied soccer violence.

In England, many hooligans were working-class men looking for a weekend fight. In Argentina, the barra bravas have ties to politicians, the police and club management, and some of their leaders have gained the admiration of young fans. Politicians tap them as a “shock force” to muscle unions backing rival politicians. Prosecutors have accused barras of killing union workers.

“On Sundays they go to the stadium and wave the flag of the club to support the team,” said Gustavo Gerlero, a public prosecutor. “During the week they are giving support to politicians and union leaders as laborers and bodyguards by the very people that theoretically should be stopping them.”

The Argentine Football Association, the sport’s national governing body, said it was concerned about the barra bravas’ role in the violence. Nizzardo and others have criticized the powerful president of the association, Julio Grondona, for not showing the will to break the barras. Grondona, 80, has led the association since 1979, when Argentina was in the midst of a bloody dictatorship. He is also a senior vice president of FIFA, soccer’s world governing body.