Seoul (CNN) An upper floor of a South Korean nightclub collapsed early Saturday, killing two people and wounding 17 others, local media reported.

The casualties in the incident, which took place in the Coyote Ugly club in the city of Gwangju, included athletes competing in the FINA World Aquatics Championships, according to South Korean news agency Yonhap.

The two people killed were both South Koreans while the injured included four Americans, two New Zealanders, one Dutch, one Italian and one Brazilian, authorities told Yonhap. It said their injuries were not severe.

The injured Americans were US water polo players, a statement from USA Water Polo said. They were celebrating the Women's National Team winning the FINA World Championship on Friday. None had life-threatening injuries.

The internal structure collapsed around 2:30 a.m local time, according to a tweet by the South Korean Ministry of Public Administration and Security.

Two people were killed when a loft in the Coyote Ugly nightclub collapsed Saturday morning.

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