The Northern Territory's environmental watchdog has reported an “uncontrolled discharge” from Vista Gold's Mount Todd mine north of Katherine.
NT News reports the state's Environmental Protection Authority said recent rainfall may have contributed to the discharge, and officers were on site to investigate.
Earlier this month Vista Gold was given permission to pump over 14gL of waste water from retaining ponds into the Edith River so it could reopen the mine.
According to the NT News most chemical contaminants will be removed from the discharge, but the water will still contain 28 times the maximum level of cadmium.
The Government said efforts were underway to improve water quality in the Edith River.
Heavy rains earlier this year also caused headaches for Queensland's mining industry, with around 20 mines discharging water into local rivers with permission from the State Government.