The operation to re-enter the Pike River mine has been delayed until the end of February.
Doors are now being constructed 10 metres inside the Pike River portal so nitrogen can be pumped inside.
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The minister responsible for Pike River Re-entry, Andrew Little, says it's a complicated process.
"The main thing about this whole project is safety, and we're going to do this the safest, best possible way," he says.
"If it takes us an extra couple of weeks to get everything absolutely right then that's what we're going to do."
The re-entry to the mine was supposed to kick off in mid-February.
The first member of the team which will enter the Pike River Mine will be one of the world's most experienced miners, Tony Forster.
He was New Zealand's chief mining inspector after Pike River, and has always believed re-entry was safe. He's returning from Australia to be the Pike River victims' families' independent advisor and their eye underground.
"It is both doable, and yes, it can be done safely," he said when his appointment was announced.
Mr Little agreed, saying in April the recovery of the workers' bodies is "feasible", but it will take work.
"All the reports say this is doable but we've got to take the right steps at the right time," he said.
"It is about the families having a chance to put to rest their loved ones.
"Next summer we'll be in a position to gauge whether and when we'll be able to go in."
But the Opposition said any decision to re-enter the mine must not put further lives at risk.
"The expert advice has always been that to re-enter the mine would put further lives at risk," National's Pike River re-entry spokesperson Chris Finlayson said at the time.
"That wasn't an acceptable risk then and until the advice says otherwise, it's not an acceptable risk now."