The mine remains unstable and work at the portal will have to be delayed by at least a week, PwC partner John Fisk, receiver of Pike River Coal Limited (In Receivership) said.

“We have been advised by the experts involved [that] the increased gas levels make it too unsafe to start work,” he said.

“This is a temporary setback but we realise the delay is frustrating for all those parties involved, especially the families and those who have spent the last two and a half months working to stabilise the mine.

“Ensuring everyone’s safety is our paramount concern. We’re committed to stabilising the mine and will continue to monitor gas levels and reassess the situation in the middle of next week.

“We have informed the families of the 29 men and will continue to provide updates on any further developments.”

A staged re-entry has already been flagged and work on placing a temporary seal 100m inside the mine is expected to start next week.

Fisk previously told ILN this effort would also involve replacing the hastily-made seal at the portal with more airtight steel double doors.

Under the conceptual re-entry plan, Mine Rescue personnel will set up temporary seals at intervals of 200 to 300 metres.

Fresh air would then be allowed into the mine up to each temporary seal as rescue specialists progressively worked their way up the tunnel.

This exercise would help identify whether the tunnel could be recovered and could allow personnel to get a better idea of how serious the roof fall was at the end of it.

About 1600m into the tunnel is an abandoned load-haul-dump vehicle.

Camera-equipped bomb disposal robots and the Western Australian Water Corporation’s tunnel inspection vehicle have failed to get around the LHD in all attempts so far.