Flammable levels of hydrogen have been found at a number of locations near the site of a controversial gas project that has been blamed for contaminating huge swathes of prime Queensland farm land.

The ABC understands an ongoing Environment Department investigation has confirmed that the contamination is much more widespread than previously thought.

The Queensland Government has dispatched Environment Department officers to the Hopeland community, near Chinchilla in the state's south, and is setting up a call centre to help explain the situation to landholders.

Hopeland is the site of Linc Energy's underground coal gasification (UCG) plant, which is alleged to have polluted soil and groundwater during its operation.

UCG involves burning coal deep underground, which creates a gas that is then collected at the surface through wells.

In 2015, the ABC revealed a confidential study commissioned by the Environment Department had found that the Linc facility had caused "irreversible" damage to strategic cropping land, with concentrations of hydrogen at explosive levels found in the soil.

Abnormal amounts of methane and high levels of cancer-causing benzene were also found.

A map showing proposed caution zone in southern Queensland in the wake of alleged pollution by Linc Energy. ( Supplied: Origin Energy )

Former Linc employees told investigators that gas often bubbled up from the ground and that they had fallen ill while working at the site.

The company, which is now in liquidation with estimated debts of $300 million, has been committed to stand trial on five counts of wilfully causing environmental harm.

Five former executives — including Linc founder Peter Bond — have also been charged with environmental offences, which can carry a penalty of up to five years' jail.

Due to fears about possible hydrogen explosions, the Government has been enforcing a 314-square kilometre "excavation caution zone" around the Linc plant, with landholders banned from digging any hole deeper than two metres.

The ABC understands further investigation by the Environment Department has now found flammable levels of hydrogen at locations outside the current caution zone.

The hydrogen has been detected underground and the department says it dissipates quickly in the open air.

Government sources have stressed the gas is not of an explosive concentration but landholders will be encouraged to exercise caution.

Environment Department testing only found hydrogen and not more dangerous chemicals at the former Linc site.

The department's investigation into Linc Energy was the largest of its type in Queensland's history.