Workers at a central Queensland coal mine where five men were nearly killed in an explosion last month have been banned from going underground.
New fears of an underground explosion surfaced at the weekend after gas levels began to rise at Anglo American's Grosvenor Coal Mine near Moranbah.
An Anglo American spokeswoman said people were stopped from going underground as part of the mine's action plan for spontaneous combustion risk after levels of carbon monoxide and other gasses began to rise.
"With the cessation of longwall mining activity after the methane ignition incident on May 6, we have been closely monitoring various gas levels to ensure the ongoing safety and integrity of the mine," she said.
"The suspension of longwall mining over time elevates the risk of spontaneous combustion, due to the oxidation of the coal in the longwall goaf environment.
"During normal longwall mining operations this risk is very low."
The spokeswoman said inert gas was being pumped into the ventilation network to reduce the risk of combustion.
"As an additional precaution we have established an exclusion zone around the entry of the mine," she said.
"No crews will return underground until the underground environment has been proven to be stable.
"Our investigation into the methane ignition incident is still under way and we have committed that we will not recommence mining until it is safe to do so."
The mine was immediately shutdown in early May after a methane explosion burnt five men, all in their 40s and 50s.
A board of inquiry was ordered by Mines Ministers Anthony Lynham to investigate the explosion.
The board, headed by retired judge Terry Martin, will report to government by November 30.