South Korean authorities were combing through mobile phone data, credit card statements and CCTV footage on Tuesday to identify people who visited nightclubs at the center of one of the capital's biggest novel coronavirus clusters.

More than 100 new cases linked to the nightclubs have brought fears of a second wave of infections in a country held up as a coronavirus mitigation success story.

Health authorities have tracked and tested thousands of people linked to the nightclubs and bars in Seoul's Itaewon nightlife neighborhood, but want to find others who they have not been able to identify.