China’s Zijin Mining Group has been reportedly asked by Serbia to stop work at the RTB Bor copper mine due to non-compliance with environmental standards.

The company has also been ordered to complete a wastewater treatment plant on priority at the mine to avoid polluting the River Pek, a tributary of the Danube, Reuters reported citing Serbian Mining and Energy Minister Aleksandar Antić.

Formerly known as RTB Bor, Serbia Zijin Bor Copper is a copper mining and smelting complex in Bor.

The RTB Bor complex has multiple mining and processing sites, which include Veliki Krivelj, Cerovo Mine, the underground mine Jama, and the smelter and copper slag processing plant.

Earlier, Zijin acquired a 63% stake in the RTB Bor copper complex by agreeing to invest $1.26bn in the project.

Last month, Serbia Minister of Energy, Development and Environmental Protection Zorana Mihajlovic said Zijin’s Serbia-based unit was ordered to cease work on its Jama copper mining shaft.

Zijin’s unit in Serbia halted work on the Jama mine’s ventilation shafts following complaints about noise levels from residents, reported Reuters.

The news agency quoted the Zijin’s unit in Serbia as saying: “The exploitation of copper in the Jama mine is ongoing, deep underground.”

Mihajlovic added: “They have until April 30 to eliminate all irregularities.”

Last week, Zijin’s Serbian unit reportedly announced plans to expand and improve environmental standards at its mines and a smelter at the Bor complex, with a total investment of $408m in this year.