The seriousness of the situation was compounded by the fact that methane seam gas emissions in the area could have proved fatal for the miners, had they been trapped for a length of time inbye of the fall.

“Asphyxiation from oxygen deficiency was possible,” the report said.

The fall occurred in the longwall development panel where the miners were working only minutes before the incident.

There was little indication of the pending failure of the roof strata until about one minute before the event, when warning triggers were noted and the seven miners, including the face deputy, were trapped at the face of the blind heading.

“They all could have been injured and trapped under the fallen ground had it not been for the limited warning they received,” the report said.

The panel development had reached 100m from the last cut through and conditions appeared to be very stable.

The fall of ground was about 25m long, 4m high and almost to the full width of the heading, and was between the miners and their only escape route.

Eventually the roof fretting ceased, the steel mesh used in the roof support system tore open and the miners escaped uninjured over the fallen ground.

The report said inadequate roof support had been installed to control the geological conditions in that area of the mine.

It also found the Mine Safety and Health Management System Principle Hazard Management Plans for Strata Control and Emergency Response had not specifically addressed this hazard and required significant review.

“The review should include a range of entrapment scenarios embracing fall of ground incidents such as what occurred in this instance, provision of respirable air and communications for assistance in the event that all the crew were trapped at the working face.”