Victoria's Environment Protection Authority (EPA) is satisfied water pumped from a flooded coalmine east of Melbourne has not adversely affected the health of waterways in the area.
The collapse of part of a river diversion on June 6 sent water into the Yallourn mine and further rainfall has hampered efforts to get damaged coal conveyors back online, with the adjoining power station again operating at reduced capacity.
The EPA gave permission for mine operators to clear the water out of the flooded mine by pumping it into the Latrobe River.
The EPA said the river is being monitored and it is satisfied mine operators TRUenergy are abiding by the conditions of the approval.
"Results have so far indicated slightly higher turbidity (cloudiness due to silt) in the Latrobe River, but no significant increases in other contaminants like heavy metals," an EPA spokesman said.
On Friday Environment Victoria raised concerns about the quality of the water being released back into the river system.
Campaigns director Mark Wakeham has called for a government inquiry.
"The site seems to be inherently unstable and is currently flooding every time it rains," Mr Wakeham said.
"We're gravely concerned about the potential impacts on the health of the Latrobe River and Gippsland Lakes."
TRUenergy said work is underway to put in a pump and piping system that will be able to handle Morwell River flows through the diversion.