According to the Daily Mail, hundreds of fans were crushed when they rushed the stage, with 47 people needing medical treatment. At one point, One Direction addressed the mob of fans, asking them to step back from the stage for safety reasons.
According to local reports, those who needed medical attention were treated for symptoms of asphyxia, which include abnormal breathing due to deficient oxygen supply.
Mario Cassareto, the head of Peru's fire service, told Peruvian radio: "We treated 47 children with the first stages of asphyxia. Everything is under control. We have nothing to be ashamed of, we've handled the situation well."
He added, "We're working with the police and the security companies [who were contracted for the show], 911 and VIP. It's under control and we are still treating those with symptoms of asphyxia that we pulled from the back."
A spokesman for One Direction noted: "The band's management employ, in their touring party, the very best crowd control and advance security specialists who plan in advance and on the day with all the relevant local experts and services including police, fire, medical, the venue and the promoter."