BUENOS AIRES, Argentina (AP) — In one of themost violent episodesin recent South American football history, hooligans from Argentina's Independiente and visiting Universidad de Chile attacked each other in the Copa Sudamericana. The ferocity of the stadium fighting with sticks and sharp objects injured nearly 20 Chilean fans while local police chose to stand down. Two of the Chilean club fans were in critical condition. The round-of-16 match on Wednesday was canceled, and CONMEBOL must decide the future of the tie. How did the violence erupt? According to a report from the Ministry of Security of the Buenos Aires province, it started among about 4,000 Universidad de Chile fans in an upper stand of Libertadores de América Stadium in the Buenos Aires district of Avellaneda. Some of them smashed bathrooms, fast food outlets and seats as soon as the match began, and then threw objects at the home fans. The Chilean fans ignored police warnings over the stadium speakers and were ordered to leave the stadium. It was then when dozens of Independiente fans blocked access to the visiting stands and savagely attacked the Universidad fans. There were no police or private security personnel in that area. Two Chileans jumped from the stands to escape the attackers. Others were left lying unconscious and covered in blood. According to the police report, 125 Universidad de Chile fans were arrested and then released. The prosecutor's office also issued arrest warrants for Independiente attackers who were identified. What penalties can CONMEBOL apply? The match was canceled with the score 1-1 and Universidad leading 2-1 on aggregate. The game will not be resumed. CONMEBOL's disciplinary unit will address the events. FIFA President Gianni Infantino called for "exemplary sanctions against the perpetrators of terrible acts." It is likely that Independiente will be eliminated from the Copa Sudamericana as CONMEBOL's statutes assign the host club the greater responsibility for the organization and security of matches. There was a recent precedent. The April match between Colo-Colo of Chile and Fortaleza of Brazil in the first round of the Copa Libertadores was also canceled before it began due to serious clashes between Colo-Colo fans and the police.Two fans were killed. CONMEBOL awarded the Chilean club a defeat and ordered it to play five home matches behind closed doors. CONMEBOL could also remove Independiente and Universidad from the Copa Sudamericana and bar both from international competitions next year. Peru's Alianza Lima awaits its opponent in the quarterfinals. What does Independiente say in its defense? The Argentine club's president, Néstor Grindetti, traveled to CONMEBOL headquarters in Paraguay on Thursday, and blamed the Chilean club. "It's clear from the images that the Chileans committed the vandalism from the start of the match," Grindetti said. Universidad de Chile president Michael Clark said, "They're not up to the task; there's a dehumanization of what happened. When they went to Santiago (for the first leg), nothing happened to them." When will penalties be announced? CONMEBOL may take several days given that the Copa Sudamericana doesn't resume for a month. "It will resolve any sanctions ... as soon as it gathers all the incident reports," CONMEBOL said in a statement on Friday. ___ AP soccer:https://apnews.com/hub/soccer