Martín Tena, 18, attended the rap concert with six friends and was on the pier when it collapsed.

“It felt a bit like being in an elevator that suddenly breaks up into two,” he said by phone, after being discharged from a hospital on Monday evening with a sprained ankle. “There was just this huge noise, of wood splintering and people screaming.”

Mr. Tena managed to climb out of the debris, but he then could not immediately find two of his friends who had apparently fallen into the water. “It seemed they might be dead and then it really felt like this was the worst moment of my life,” he said. But his friends survived the ordeal.

The organizers of the festival said in a statement on Monday that their concerts “fulfilled the security conditions required by the law.”

An investigation is underway to determine the causes of the accident, but several politicians had warned in recent months that the pier needed work.