The death toll from an indoor shooting range fire in the southern port city of Busan has risen to 12 after Kazunobu Nakao, a 37-year old Japanese tourist who was being treated for severe burns, died of heart failure on Sunday.

The deadly blaze has so far claimed the lives of eight Japanese and four Koreans. Busan police say four others are being treated for burns at a local hospital with three of the patients in critical condition.

A police investigation of the exact cause of the fire continues.