The underground explosion at a Queensland coalmine that has left five men fighting for their lives could have been far more catastrophic, a union boss says.

The miners, aged in their 40s and 50s, suffered extensive burns to their upper bodies and airways in Wednesday’s blast at Anglo American’s Grosvenor Coal Mine at Moranbah.

Four of the workers are in critical condition in the Royal Brisbane and Women’s Hospital, with a fifth listed as stable.

CMFEU boss Steve Smyth says it’s sheer luck the gas explosion wasn’t as devastating as the 2010 Pike River Mine disaster in New Zealand, which killed 29 men in a series of blasts.

Mr Smyth said Anglo American has the worst safety record in Queensland, with the largest number of fatalities of any operator since 2000, and the explosion had to be the result of systemic failures.

“Stop beating around the bush and bull****ting us with buzzwords. Just call it for what it is,” he said.

“Gas ignition is usually like lighting your barbeque – you light it and it goes poof. But this was like the whole barbeque exploding,” he told AAP on Thursday.

“That’s not very common.

“People might say we are making more of this than what it is, but this was very, very serious, as shown by the injuries of those five men.”

Anglo American had received a stream of complaints about mine safety, the CFMEU says. Photo: AAP

Inspectors are waiting to enter the mine, which will remain closed until gas levels stabilise, and are expected to meet with Mines Minister Anthony Lynham who has flown to Moranbah.

Mr Smyth said employees had previously raised numerous concerns about the amount of gas and other work practices at the mine.

“My understanding of the concerns is that they have been raised, sometimes on a shiftly, daily basis,” he said.

All underground workers at the Grosvenor mine were labour hire or sub-contractors, and that compromised their ability to be vocal about safety concerns, he said.

The Queensland government is considering establishing a board of inquiry, with public hearings, to determine what happened.

Chief Inspector of Coal Mines Peter Newman said the company “informed us that there had been an ignition of gas on the long wall face”, but there was little additional information about the cause.

He said inspectors had communication with the mine last month.

Asked if any safety issues were identified, Mr Newman said: “Whenever you bring a fresh pair of eyes to an operation, there are always either recommendations for improvements in certain aspects of the mine, or at the worst case, a directive in terms of the mine taking particular action.”

Annastacia Palaszczuk has limited her comments to sympathy and concern for the injured miners. Photo: AAP

He did not directly answer when asked if Wednesday’s incident was related to concerns previously raised with the mine.

Premier Annastacia Palaszczuk also refused to speculate on the cause.

“The mines have a duty of care to ensure their workers go to work safely and return home safely, and this has not happened in this case,” she said. “Our thoughts are with the families.”

In a statement issued on Thursday, Anglo American said support was being offered to the injured miners and their families.

“We are all devastated and we don’t yet understand what caused this incident. Once it is safe to return underground, we will commence an expert technical investigation to ensure we understand what has happened,” said Tyler Mitchelson, chief executive of the company’s Metallurgical Coal business.

The incident comes months after a report found Queensland’s mining sector was in the grips of a death cycle, with more lives at risk without a safety overhaul.

The report reviewed the 47 deaths in the state’s mines and quarries from 2000 to 2019 and made a series of recommendations after finding most of the deaths were entirely preventable.

-AAP