Three managers of Zijin Mining, China's largest gold producer, have been detained in relation to an acid leak that affected thousands of people and poisoned nearly 2,000 tons of fish.
Wastewater containing acidic copper leaked from the mine in Fujian province on 3 July, contaminating the Ting River.
Zijin Mining, which disclosed the spill to its investors nine days after the accident, is being probed by the China Securities Regulatory Commission.
The Chinese Government said the leak-proof barrier was broken in a waste pit due to heavy rainfall, and water containing acid copper seeped into the Ting River via an illegally built drainage.
The company has been ordered to suspend production by the environment ministry and provincial officials saying it needs a major overhaul of its system to safeguard against spills.
A joint investigation conducted by the Fujian provincial and Longyan municipal environmental protection authorities showed 9,100m3 of leaked wastewater flowed through the illegally built passage into the Ting River between 3-4 July.