Five people have died and five more are in critical conditions after attending Time Warp in Argentina, according to reports from the BBC.
Alberto Crescenti, the chief of the medical services organization SAME, confirmed to the BBC that the victims were between 21 and 25 and were suspected of acute poisoning at the festival.
"We'll see what substances they took," Crescenti said to the BBC.
The deaths happened on the first night of the festival, which was taking place in Costa Salguero in the Argentinian capital of Buenos Aires.
The festival has been cancelled with the organizers issuing the following statement: "Our thoughts go out to the families and friends of the victims. We are taking the time to determine the cause of this tragedy. Tonight's festival has been cancelled. We are working quickly to ensure that everyone is reimbursed for their tickets. We ask everyone to keep their thoughts and prayers with those who lost their loved ones."
Attendees had reportedly previously complained of overheating, overcrowding, and poor ventilation at the festival.