China's environment ministry on Monday criticised state-run metal producers China Gold and CNMC for polluting their surroundings and failing to adequately address previously identified problems, with a particular focus on tailings dams.

The Ministry of Ecology and Environment said last month it would send inspection teams to China National Gold Group and CNMC, or China Nonferrous Metal Mining Group Co, in the central government's latest round of audits aimed at cleaning up heavy industry. 

Inspectors found flue gas leaks from a copper smelting furnace belonging to CNMC unit China Daye Non-ferrous Metals Mining 0661.HK , in Hubei province, as well as excessive concentrations of toxic impurities lead, arsenic and cadmium in a nearby rainwater pipe network, a ministry statement said.

Daye Nonferrous, one of China's biggest copper producers, also failed to build a flood interception ditch for a tailings dam at its Fengshan copper mine despite being told to do so as far back as 2012, the ministry said, adding that the dam was only some 800 metres from the Yangtze river.

Tailings dams are commonly used by mining firms to store waste remnants of ore. They have been under close scrutiny globally since the 2019 collapse of one in Brazil which killed around 270 people. 

Daye has over the years dealt with calls for it to rectify outstanding environmental problems "in a perfunctory manner", the ministry said.

Daye and CNMC did not immediately respond to requests for comment.

The ministry's report on China Gold centered on its operations in the southern regions of Yunnan, Guangxi and Guizhou, which were described as being rich in minerals but having fragile ecosystems.

In Guangxi, inadequate work on tailings dams belonging to a unit of China Gold had created reddish-brown ponds with excessive levels of arsenic and cyanide, the ministry said.

China Gold did not immediately respond to a request for comment on the findings.

(Reporting by Tom Daly; editing by Jason Neely) ((tom.daly@thomsonreuters.com; +86 10 5669 2119;))