DRILLING fluid from one of the state's most ambitious coal-seam gas projects has forced a Queensland Department of Environment investigation into mining giant, QGC.
The material entered the Condamine River as QGC contractors drilled a pipeline underground 12km downstream of Chinchilla Weir.
The underground line will run for 540km connecting Queensland gas fields to Gladstone where the gas will be processed at a Curtis Island plant.
The Condamine River forms part of the Murray-Darling Basin river system.
Environment and Heritage Protection Minister Andrew Powell said his department was investigating.
He said it was an immediate response after QGC notified the Government of the incident.
"Although (environmental) officers who inspected the site did not see any significant water quality impact, they are taking steps to address the risk of future potential impacts," Mr Powell said.
A limited amount of the drilling fluid seeped from the drill hole up onto the bank of the river and then into the river.
There it was contained within a wall of sandbags and pumped out.
The contractors have stopped drilling work at the site.
QGC has already signed $100 million in LNG supply contracts.