International experts say Solid Energy should get back in to the main tunnel at Pike River mine on the West Coast where 29 workers were killed in explosions in 2010.
Two men with decades of mining under their belts have looked at the re-entry plan and say its feasible and not as risky as owner Solid Energy fears.
Solid Energy is worried that someone could die during the re-entry operation, but will make a decision later this month on whether it goes ahead.
The state-owned company first aired its safety concerns last month. At the time, chief executive Dan Clifford said the single entry design increased the risk to life, the rock tunnel had suffered enormous stress following four explosions and a geological fault meant the walls and roof were fractured.
"The nature of what we're dealing with up there isn't just a simple rock tunnel. We have poor roof conditions, we have gas, we know - or we suspect anyway - that the roof has been damaged."
Mr Clifford said that while people would have opinions, Solid Energy's opinion on re-entering the main tunnel was the only one that mattered.
Bob Stevenson and Dave Creedy were hired by the families of those who died more than two years ago and both have extensive mining experience.
Mr Stevenson was the United Kingdom's Chief Mines Inspector. He believes the main tunnel could be flushed out of methane without anyone having to go inside as it would be done by people working in difficult terrain on the Paparoa ranges above the tunnel.
He said there would be risk for people working on the surface, as access to the ventilation points in the hills above the mine involves using helicopters. The aircraft would be used to "take equipment up to lay the nitrogen line, to take staff up to the return shaft. So there is risk from use of helicopters".
Mr Stevenson said once it is ventilated, mines rescue staff could get 1.7 kilometres into the tunnel before the condition of the roof and walls become an issue.
"So you could have a respirable atmosphere without any people going underground whatsoever. I would like a quick inspection as far as we can. If it's to the 1700-metre mark at least it gives us some information to make a further judgement, a sound judgement."
The families' experts and representatives of Solid Energy held a teleconference yesterday. Bob Stevenson said he can't talk about what was discussed, but said both he and Mr Creedy believe that re-entry is feasible.
In a statement, the SOE said Solid Energy is "talking direct to the families' group about this and that the process of getting to a decision is being discussed. We will not be making any other comment until after a decision has been made."
Families have faith in experts - Monk
A spokesperson for some of the Pike River families, Bernie Monk, says they absolutely trust the word of the Bob Stevenson and Dave Creedy.
"If Bob and Dave ever came back to the families and looked me in the face and said to me this job can never be done we would walk away and we've always stuck together on this.
"They've said to me even before the meeting, Bernie this job can be done and it can be done safely without anyone being hurt in this."
Solid Energy has already said that if legal advice states a second access tunnel is a legal requirement to any re-entry plans, it will be the end of the project.
Mr Monk said the families have hired another expert to advise on the issue of whether another means fo access is legally required for re-entry.
"Safety is the top priority and this is where we we're coming from and we want a make sure that this happens too. It's not all about rip, shit and bust here - it's make sure that everything is done above board and, and everyone - and all the questions are answered."
The stakeholding ministers in Solid Energy are the Ministers of Finance and State Owned Enterprises. Each year those ministers send letters of expectation to Solid Energy setting out what they want it to achieve.
Health and safety experts have told Radio New Zealand that if the ministers were to say they wanted the SOE to act in the public interest and facilitate re-entry, then the board would have to try to accommodate.
The directors, though, would still have the right to decline to sign of on something that was illegal or against legal advice.
Letters of expectation for the 2015/16 year have not yet been considered by the ministers.
The next Solid Energy board meeting is scheduled for 29 October, but the company said it is possible there would be a special one held for this decision.