Chinalco Mining has shut down operations at its Toromocho copper mine in Peru after the country's environmental regulator found that it was contaminating two lakes.
The regulator said the company was generating "acidic effluent" in the lakes high in the Andes in the district of Morococha, 150 kilometres east of Lima, where the open pit mine is located. It issued a statement later on Saturday saying that the company had complied with its order to stop discharging the waste.
A source at the company said: "We carried out the order on Friday when it was communicated to us. Operations are suspended."
The company would investigate and take action in the next few days, the source added.
The contamination was discovered during inspections two weeks ago, the regulator said. "This preventative measure seeks to mitigate the environmental impact that is being generated by the emptying of effluents from the West waste deposit into the lakes and from a drainage system" into one of the lakes, it said.
A video on the regulator's web page viewed by government workers appeared to show yellowish water running down a hillside into a blue lake.
Chinalco Mining controls the Toromocho Project in the centre of the South American country, one of the largest pre-production copper plants in the world.
Toromocho began operations in December after investing US$4.8 billion in the mine.
It is expected to produce around 300,000 tonnes of copper annually when running at full capacity.
Peru is the world's second biggest copper producer.
Additional reporting by Agence France-Presse