An exclusion zone has been set up after repeated gas incidents at a Queensland coal mine.

The exclusion zone is now in place at the entry to the Grosvenor Mine, near Moranbah, after increased levels of carbon dioxide and other gases were detected in recent days.

It is the same mine where five workers were critically injured in a gas explosion last month. Production at the Grosvenor mine was paused on May 6 after an underground methane gas explosion injured five men, four of which remain in a Brisbane hospital in a stable condition.

Mine owner Anglo American says it has been monitoring levels of gas since work stopped.

“Consistent with our risk management protocols, we made the early decision to fully restrict access to the mine when levels of certain gasses started to rise,” the company said this week.

“Over the past couple of days, we commenced a range of measures to stabilise the area,” CEO of Anglo American Metallurgical Coal, Tyler Mitchelson said.

“Once gas levels are proven to be stable, work will continue to ensure the ongoing safety and integrity of the mine.

“In the meantime, we will continue to keep our workforce closely updated.”

Meanwhile, the Mines Inspectorate is investigating a power interruption at Anglo's Grasstree Mine on June 6, which stopped a main ventilation fan.

David Cliff, a professor of Occupational Health and Safety in Mining at the University of Queensland says some risks rise when work stops.

“When the longwall stops, you've got broken coal and you're still ventilating and air is going through, so it's exposed longer than normal,” he said.

“That increases the risk of the coal reacting and generating heat and then getting to flame temperature and combusting.”

The CFMEU says workers at all three Anglo American underground coal mines in Central Queensland have expressed fears for their safety.

“We believe Anglo's lost control of their mines,” CFMEU Mining and Energy Queensland President Stephen Smyth has told the ABC.

“They're going from one potential disaster to another in the way they're managing methane gas and how they're managing the hazards at their coal mines.

“They could have followed another of number of other measures prior to that and they wouldn't have got themselves in this situation … where they've got another potential spontaneous combustion event.”

Workers at the Moranbah North mine have been protesting outside the site, accusing management of refusing to discuss safety issues.