Mines Rescue Service personnel, lawyers for the families of the Pike River victims, police representatives and Pike River Coal receivers met this week in Christchurch.

"What was agreed to was that parties would be involved in putting together feasibility studies around the various options that have been mooted for re-entering the main area of the mine," Pike River Coal receiver Malcolm Hollis told Radio New Zealand.

There are concerns over who will fund the feasibility study alone.

Key did not rule out contributing to this study, according to the radio network, but he also had safety concerns over re-entering the mine.

“The international mine inspectors we’ve spoken to have said in some instances you can never get in mines,” Key reportedly said.

The rockfall at the end of the 2.3 kilometre access tunnel is reportedly about 50 metres.

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.

Pike receiver John 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 200-300m.

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.

The extent of the roof fall could determine how feasible it is to recover the 29 bodies in the mine.

“If there is a significant roof fall there then we will need to put a permanent seal at the end of the tunnel,” Fisk previously told ILN.