A sodium hypochlorite tank of Shandong Haihua Group Co., Ltd's plant in Weifang City, suddenly burst at around 6 AM, leading to a leak of the irritative chemical which can cause discomfort in the respiratory system. The chemical is usually used as a fungicide and an oxidizing bleach.A total of 58 company staff went to hospital for checkup and treatment. As of Wednesday evening, 26 remained in hospital.