Queensland's Department of Environment says it is not ruling out an underground fire as the cause of gases detected just below the soil surface near Chinchilla, on the western Darling Downs.

The department has revealed that preliminary tests carried out last week at two private properties at Hopeland, near Chinchilla, showed a positive result for carbon monoxide, hydrogen and hydrogen sulphide.

"The gases identified are commonly associated with combustion and are not associated with coal seam gas development," said Jon Black, the director-general of the Department of Environment.

The Hopeland area is the site of coal seam gas facilities and was the location of an underground coal gasification pilot plant run by Linc Energy.

Underground coal gasification (UCG) is a controversial technique involving the ignition of the coal seam, with oxygen pumped into a well to allow for the combustion of the coal, which then produces gas.

The Linc Energy UCG project is now the subject of court action by the state environment department, which alleges the UCG operation near Chinchilla caused serious environmental harm.

The company last year rejected the charges as "misguided".

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The ABC understands one of the charges relates to a so-called overburden fracture, a crack in the layers of rock and soil that sit above the coal seam.

Asked if the recent discovery of gases near the surface of properties at Hopeland was related to the alleged underground incident involving the Linc UCG project, the department acknowledged "there is an ongoing prosecution of Linc Energy", and as such it could not comment further.

The ABC also asked if an underground fire was the most likely cause of the gases moving towards the surface.

"Given the nature of the gases found, [the department] cannot rule out an underground fire as a cause, however at this early stage of the soil sampling, [the department] has not been able to determine the actual source or cause," the department said in a statement.

Linc Energy has told the ABC that it was only told about the gas findings 10 minutes before the department publicly released them.

"We are concerned that the department's release may cause an inference to be drawn that these [gas] readings were in some way related to the company's Chinchilla operations," a spokesman for Linc Energy said.

"Linc Energy will continue to monitor this matter closely and seek further information from the department."

Queensland Health has assessed the information from the preliminary tests and has determined that there are no health risks to landowners at this stage.

"Independent environmental experts have advised that because the gases are in the subsoils, immediate impacts to grazing animals and stock are extremely unlikely," the environment department added in its statement to the ABC.

But the Lock the Gate Alliance has warned that the gases found, including carbon monoxide, hydrogen and hydrogen sulphide, "are explosive and farmers in the Hopeland area have been advised not to excavate or disturb soils greater than two metres deep without talking to the department".

"This incident confirms that underground coal gasification is a dirty, polluting industry that should now be permanently banned in Queensland," alliance president Drew Hutton said.