The environmental protection chief of a city in south China's Guangxi Zhuang Autonomous Region has been dismissed following the contamination of one of the city's rivers, local authorities said Friday.

Wu Haique, head of the environmental protection bureau of the city of Hechi, was removed from his post at the fifth session of the Standing Committee of the third Hechi Municipal People's Congress.

The decision was reached after a vote and was based on a suggestion by a joint investigation team formed by the regional government.

Another four officials from the Hechi municipal and Jinjiangcheng district environmental protection bureaus, as well as two officials from district business bureaus, were dismissed from their posts.

Two more officials, including vice mayor of Hechi Li Wengang and deputy Party secretary of Jinchengjiang district Wei Yongfu, were given demerits.

An investigation into possible corruption or other malfeasance surrounding the incident is under way, said Lei Yongda, a member of the standing committee of the regional discipline inspection commission and the deputy director of the regional department of supervision.

Cadmium contamination on the Longjiang River was first detected on Jan. 15 after fish died in large numbers. Ongoing cleanup efforts will run until the end of February. As of Thursday, cleanup procedures had brought the cadmium concentration peak down from 80 times the official limit to 20 times the limit, experts handling the incident said.

Fishermen from Hechi, as well as Liujiang and Liucheng counties in the downstream city of Liuzhou, have been prohibited from selling farmed and wild fish from the Longjiang River.

The Longjiang is an upstream tributary of the Liujiang River, which runs through Liuzhou, a city with 1.5 million permanent residents.

As of 6 a.m. Tuesday, water produced by four major water plants in Liuzhou was up to standard, with cadmium concentrations no higher than 0.00065 milligrams per liter, according to the latest available water quality tests.

All seven of the heavy metal production plants located upstream have suspended operations so to curb potential sources of new pollution.

So far, nine chemical plant executives have been detained in connection with the incident.

Cadmium is a carcinogenic chemical mostly found in industrial effluents.