Queensland's environment department is investigating claims mining company New Hope expanded existing operations at its New Acland coal mine without permission.
The state environment department confirmed it is investigating New Hope's controversial mine, west of Brisbane, but the company insisted the complaints were part of a campaign against it.
It comes as a protracted legal battle rages over the proposed stage 3 extension of the mine, near Toowoomba.
The Oakey Coal Action Alliance is appealing a Queensland's Supreme Court decision to reverse an earlier decision scrapping the stage 3 expansion.
Paul King, president of the Alliance, said they were happy the department had taken their concerns seriously.
"Stage 2 of the Acland mine has had dramatic impacts on our community, that is why we have objected to its Stage 3 expansion," Mr King said.
"Now New Hope is circumventing due process and mining wherever they want anyway."
The miner strongly denied those allegations, claiming in a statement the complaints were tied to the legal challenge to stage 3.
"New Hope find it generally disappointing that OCAA (with the support of the Environmental Defenders Office), after being unsuccessful in the judicial review proceedings, are now bypassing the Land Court and remaining statutory processes in an attempt to stop the project," a spokesperson said.
In their appeal, the Alliance argued the ruling that groundwater impacts can't be considered in mining objection hearings opens a Pandora's box for future objections, not just the New Acland project.