An accidental explosion of an unknown powder set off the fire near the stage in front of about 1,000 people, said Wang Wei-sheng, a liaison with the New Taipei City fire department command center.
Taiwan's Central News Agency reported 349 have been injured, quoting the Health Ministry. They included four mainland Chinese and two foreigners.
Wang said 83 people had serious injuries.
The stage caught fire at the Formosa Water Park in New Taipei City near the island's capital and was quickly brought under control.
Video showed rescue workers and bystanders carrying burned and injured people on their backs, in inflatable boats and on stretchers to get medical treatment.
CNA reported witnesses as saying the fire spread quickly after the colored powder was blown into the air.
It wasn't clear if the colored powder was part of a performance. The cause of the fire is being investigated.
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