Three managing personnel of a copper plant have been detained and a county official has resigned after the plant contaminated a local river in Shanghang County, east China's Fujian Province.

Lin Wenxian and Wang Yong, head and deputy head of the plant owned by Zijin Mining Group Co., China's leading gold producer, as well as Liu Shengyuan, who was put in charge of the plant's environmental protection, have been detained by the public security bureau of Shanghang County, said Wen Songxing, commissar of Shanghang County Public Security Bureau, at a press conference held Thursday night.

Chen Jun'an, head of the county's environmental protection bureau, resigned in the wake of the river pollution incident, said Liang Basheng, deputy head of Shanghang County Government.

Pollution from the copper plant has severely contaminated the Tingjiang River, killing fish in large quantities.

A joint investigation conducted by the Fujian provincial and Longyan municipal environmental protection authorities showed 9,100 cubic meters of waste water leaked from the sewage tank flowed through an "illegally built passage" into the Tingjiang River between 4 p.m. July 3 and 2:30 p.m. July 4.

The county's public security bureau has begun further investigation over the incident.