Australian mining company Linc Energy is facing allegations of exposing workers to dangerous gases at its demonstration facility located near Chinchilla west of Brisbane in Queensland.
Based on an internal government briefing document seen by the ABC, an investigation revealed workers claims they have suffered ill health following a series of 'uncontrolled release' of gas at the plant between 2007 and 2013.
The symptoms are said to be consistent with exposure to the chemical constituents of the hazardous gas, according to a medical expert commissioned by the department who reviewed workers' statements and medical records.
Syngas contains toxic carbon monoxide, benzene, toluene and other substances. It was produced at the plant by burning subterranean coal seams in Underground Coal Gasification (UCG) process.
The plant began operating in 2007, with Linc starting decommissioning in 2013.
Following the release of the toxic gas, the environment at the site was polluted, ABC said.
Approximately 90 former employees and consultants of Linc were interviewed in the report, stating that the raids were carried out when the environment department obtained information from various confidential informants about incidents taking place at the site from 2007.
The document stated that that the release of the gas into the surrounding air was due to rock fractures and contaminated the groundwater by syngas and syngas by-products.
First gas from Linc's Chinchilla demonstration facility was produced from July 1999 when it was started.
UCG is an industrial process which converts coal into product gas and is carried out in non-mined coal seams using injection of oxidants, and bringing the product gas to surface through production wells drilled from the surface.
The technique can be applied to coal resources that are otherwise unprofitable or technically complicated to extract by traditional mining methods and has been linked to various concerns from environmental campaigners.