A soccer game near Argentina’s capital, Buenos Aires, was unexpectedly canceled on Wednesday night after violence in the stands left some fans hospitalized or detained by the local authorities.

The match in the city of Avellaneda between an Argentine club, Independiente, and a Chilean one, Universidad de Chile, was canceled because of a “lack of security guarantees,” Conmebol, the organization that regulates soccer in South America, said in a statement.

It was unclear what exactly sparked the violence at the stadium, the Estadio Libertadores de América. Independiente said on social media that the teams had moved to the locker rooms after “disturbances” in the visiting club’s stands. Universidad de Chile said on social media that fans had been “brutally attacked” at the stadium.

President Gabriel Boric of Chile said that Chilean citizens — he did not say how many — had been hospitalized after being attacked, and that some had been detained by the Argentine authorities. He instructed the Chilean ambassador in Argentina to visit Chilean citizens in the police station and at the hospital.

“What happened in Avellaneda between the fans of Independiente and Universidad de Chile is wrong in so many ways, from the violence in the stands to the obvious irresponsibility in the organization,” Mr. Boric wrote on social media. “The justice system must determine who is responsible.”

The game, part of the round of 16 for the Copa Sudamericana regional tournament, was tied 1-1 when it was abruptly cut off.

The Copa Sudamericana is the second-most important tournament in South America for club teams across the region. The winner qualifies for the top-tier Copa Libertadores and the right to be called South America’s best club.

Argentina has tightened access to soccer stadiums in the past two decades to stem violence between rival fans at matches in its domestic league. In some cases, fans from visiting teams have had limited access to stadiums, reducing the chance of confrontations. But Wednesday’s game would not have fallen under the same rules.

In May, the Argentine government shared a list of 15,000 people it had banned from games with U.S. officials ahead of a major soccer tournament. It will likely do the same ahead of the World Cup, which will be held in the United States, Mexico and Canada next year.

This is a developing story.