A Shanxi mayor has issued a public apology for waiting days to report a toxic spill into a river that serves as a source of drinking water for hundreds of thousands of people. The statement by Changzhi Mayor Zhang Bao follows a days-long public uproar over the aniline leak at a chemical plant on the Zhuozhang River last Monday, which was not publicly disclosed for five days. "I deeply apologise for this, which was the result of insufficient understanding and vigilance about environmental pollution events," Zhang said, according to the People's Daily website. Zhang's apology comes amid widespread internet criticism of acting Shanxi governor Li Xiaopeng , the son of former hardline premier Li Peng , who was already under fire for authorities' reluctance to confirm a deadly Christmas Day explosion at a Linfen construction site. In the Changzhi case, authorities did not notify residents about the nine-tonne chemical leak until Saturday, when Handan city, downstream in Hebei province, suspended water supplies, triggering panic buying of bottled water. Changzhi authorities had previously denied any reporting delay, saying they were not obligated to issue a warning until pollutants had spread beyond their jurisdiction. Zhang also said the city did not feel that notifying the provincial government was necessary at first, because they only knew of 1.5 tonnes of the chemical leaking into the river. River-water samples taken near the Shanxi and Hebei border reached nearly 720 times the accepted level of aniline at one point, Xinhua said. The benzene derivative is considered a probable carcinogen and can cause liver and kidney damage if consumed in large amounts. State media reported that four senior officials - including the general manager - at the Tianji Coal Chemical Industry plant, where the spill occurred, were sacked on Sunday. Many mainland internet users said the sacked employees were scapegoats used to protect government officials, including Li Xiaopeng, who had pledged zero tolerance for cover-ups after at least eight were killed in the Linfen blast. One commentator compared Li's situation to that of former Shanxi governor Meng Xuenong , who resigned after a waste reservoir at an unlicensed Linfen mine failed, swamping a village and killing more than 267. "Some netizens suggest you should learn something from what Meng Xuenong did," the internet user wrote. "What do you say?"