The manager, deputy manager and head of environmental protection at the Zijin-operated copper mine are in custody, Shanghang County authorities said in a statement.
Zijin, China's third-largest copper producer, blamed the leak from a sludge pond on rains that have pounded Fujian for the past few weeks, saying it responded immediately to the mishap and controlled the spill within 24 hours.
The company has pledged compensation for fish farmers who were affected. Production at the mine has also been suspended.
Investigators have found that 9,100 cubic metres of wastewater leaked from the sludge pond through an “illegally built passage” into the Ting River.
Experts believe that such an amount of waste could have leaked into the river only over weeks. Some media are reporting that two spills had already occurred in June.
Local fishermen said that last month the river turned a dark colour and fish began to die.
The company was under the obligation of treating waste rather than dump it into the environment. Instead, it deliberately chose not to disclose the disaster until at least nine days after it happened early this month.
The Environment Ministry ordered the company to upgrade its sewage-treatment system to avoid more spills.
The case highlights an inherent flaw in China’s unbridled economic growth, achieved at the expense of the environment, with major damage to the country’s water resources and soil.
More than 200 million Chinese currently do not have access to safe drinking water, according to government data.
In rural areas, residents have often reacted angrily to similar episodes and demanded polluting factories be shut down. More often than not, police and local authorities have sided with companies.
This time the authorities appear eager to act. The People’s Daily, the official mouthpiece for the Chinese Communist Party, slammed Zijin for its inaction.
Meanwhile, the company has taken a beating in the markets. The company was forced to suspend trading on its stock in Hong Kong on Monday and its share price fell 12 per cent the next day. In Shanghai, it lost 6.5 per cent.