Authorities in Chile used water cannon against crowds on Tuesday night, after some 4,000 people forced their way into a Daddy Yankee concert, police said.
Barriers were torn down, staff attacked and cars outside Santiago's national stadium damaged, officers reported.
Videos on social media show concert goers running through security gates and joining a crush of people inside the venue.
Two private security firms are facing criminal charges, local media reports.
Eduardo Vergara, a minister with Chile's crime prevention department, criticised the organisers of the event, saying they should have been in charge of security. But instead, he said, Chilean police forces had to "patch up" the gaps in security.
Mr Vergara said there will be an investigation into whether the event organisers complied with their safety requirements, such as having enough security guards at the venue.
In a statement, organisers Bizarro Live Entertainment said "the show was carried out under a strict security and logistics protocol".
The company also said that it had doubled its staffing levels and planning efforts "to deal with the wave of violence and crime that [we] have experienced lately at the massive events in our country, including the appearance of organised gangs dedicated to counterfeiting tickets and coordinating avalanches at doors".
One video on social media shows security attendants trying to stop people from getting through the gates, but they are pushed out of the way. Another video shows people climbing over barricades to get into the concert.
Authorities said that the thousands of people who entered without tickets meant the venue was over crowded, emergency clearways were blocked and people who held valid tickets were unable to get to their seats.
Some fans left before the show began because of safety fears, local media reported.
Daddy Yankee, a hugely popular Puerto Rican rapper, still took to the stage, to rave reviews, and will perform again at the stadium on Wednesday and Thursday night.
Additional reporting by Tiffany Wertheimer