A successful Official Information Act request by television current affairs program Campbell Live has unearthed a WorkSafe and Mines Rescue assessment that re-entering the mine was technically feasible.

“The document goes on to say that there are no technical or safety barriers standing in the way,”3 News reported.

“The worst part of this information is that Solid Energy was given this information almost a year ago.”

Greymouth mayor Tony Kokshoorn said the families of the victims had been led to believe that it was not safe to re-enter the drift access tunnel.

"That has turned out to be a lie, so I'm saying to Solid Energy: get down that drift and eliminate any possibilities of bodies down there," he said, according to 3 News.

According to Associated Press, Solid CEO Dan Clifford said the evaluation process over re-entering the mine would be finished at the end of October.

In a statement released by Solid, he detailed the project risks – which is designed to go up to the rockfall that has blocked off the drift 2.3km in.

Among the concerns was the single entry factor, which is compounded by the fear that another rockfall could occur.

“I’ve heard people say that this is just a big tunnel built in strong rock so there’s little chance of anything going wrong there,” he said.

“That is simply not correct. We know that the roof has already fallen at the top end and we suspect there has been a more recent fall further out.

“We know that it has been subject to enormous stress, with four explosions. We know that in the last 300m it is not strong rock. It passes through a major geological fault where all the surrounding material is fractured. We know that the type of rock changes to sandstone in places and the drift passes through a coal seam. You look at all that, and it would be just foolhardy to say this is a simple rock tunnel.”

He also discussed the risks of the gassy coal mine on the other end of access tunnel-blocking rockfall.

“Again, people look at the conceptual plan and say, well you just block that off with your temporary seal and it’s not an issue any more, but again that’s not correct.

“That seal, even with a perfect placement, will still leak. Making sure no methane leaks into the area where people would be working and no oxygen leaks back through into the old mine workings will be incredibly complex.

“We will need to continually balance the pressure on both sides of that seal for many days or weeks and use an inert gas to create a barrier between the oxygen and methane and that will rely on several things and people all working exactly as planned.

“There are many things which might go wrong with this, including not being able to get people up onto the mountain because of bad weather, or the generators failing and losing electricity up there, or losing electricity to the fans at the bottom.

“All these things have happened in the past, so we need to plan for them. Obviously, if the drift was open and clear we would have time to safely pull the team out if one of those things went wrong but, again, what about if they were trapped and we no longer had sufficient control of these elements and started to get toward an explosive mixture again in the mine?

“It’s another complication that needs to be considered because it is possible this would happen and if it happened, people could be killed.”

The CEO discussed the methods being used to minimise the possible risks, a process that has already taken many months.

“So far we are looking at more than 600 controls being in place and all of them working correctly even before anyone starts into that drift. You can’t just say, `she’ll be right, we’ll deal with it when we get there’.

“We’ve looked hard at all these potential complications and challenges and worked out how to avoid them happening, or reduce the chance of them happening, and what we might do if they did happen,” Clifford says.

“The question is not whether the job can be done. It is whether, when you look at all the remaining risks even after all your controls are in place, you are prepared to accept that risk to your people and that is the call only Solid Energy can make.”

A year ago the New Zealand government announced it would fund the $NZ7.2 million ($A6.5 million) project to conduct a staged re-entry into the mine’s rockfall-blocked drift access tunnel.

Solid Energy bought the former Pike River Coal business in July 2012.

Explosive risks from the gassy mine workings threaten any effort to possibly recover bodies of the 29 men killed by the 2010 disaster.