A government pathology report into a fish kill in the Bremer River last month revealed the dead fish showed signs of heavy metal poisoning.
The pathology report found there was evidence of toxicity in the fish and the river should be tested for cadmium and mercury.
Last week, the Defence Department admitted those chemcials, along with sewage, nickel and chromium, had leaked into Warrill Creek from RAAF Base Amberley's treatment plant.
Warrill Creek runs into the Bremer River. However ths Department of Environment and Resource Managamenet (DERM) rejected a link between the fish kills and the RAAF Base's contamination.
The report into the fish kill points to "pathological evidence of a toxin exposure or toxic process in primarily the kidney and the liver cells."
"Source toxin could be in Bremer River or prior to fish entering the Bremer River," the report said.
"There is an indication for further investigation into possible presence of toxins in the location of the fish kill."
The report then recommends water samples be tested for algal toxins, pesticides and other pollutants such as mercury and cadmium.
However, DERM Regionals Services director Randall Hart said the repoert "did not present any results of concern."
"Taking into account all of these evidentiary factors, DERM believes it is unlikely that the August incident was as a result of any releases from the Amberley sewage treatment plant," Mr Hart said.
"Water testing was carried out and it did not show any contamination of heavy metals."
Bremer Catchment Association president Nick White said if the contamination from Warrill Creek had flowed into the Bremer River, it could have dire consequences for those who use the river.
"With what's been happening at Amberley and the fish kills we've had in the Bremer River recently, I think it shows more rigorous, regular testing is necessary," Mr White said.
"People pump from the river for irrigation - for schools, parks, and backyards - so if there is heavy metal contamination, who knows what it is doing to the land it's irrigating."
The Defence Department was approached for further comment on their water testing at RAAF Base Amberley but was unable to respond on Sunday night.
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