Families have come out from the Pike River Mine, celebrating a successful re-entry nine years after the disaster.

Prime Minister Jacinda Ardern said yesterday that the re-entry "was symbolic".

Ardern visited the mine entrance earlier this month for a ceremony with the families of the 29 men who lost their lives in the November 2010 explosion.

The Pike River Mine Recovery team break through the seal at Pike River Mine today. Photo / Supplied
The Pike River Mine Recovery team break through the seal at Pike River Mine today. Photo / Supplied

Ardern said yesterday that entry to the mine drift today was something best left to the families of the men who were killed there.

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Media were not allowed to attend.

The group representing 29 of the Pike River Families - the Pike River Family Reference Group - has welcomed the unsealing of the mine at a private family event this morning.

Group member Anna Osborne, who lost her husband to the mine explosion, described the opening of the doors as "incredibly emotional".

"Watching those doors open and seeing the light enter that dark tunnel for the first time in years was incredibly emotional. We've known we are going back in for a year now, today it feels like it.

"This is the start of a journey that will end with truth and justice."

Family Reference Group Chair Anna Osborne and mine worker Shane McGeady. Photo / Supplied
Family Reference Group Chair Anna Osborne and mine worker Shane McGeady. Photo / Supplied

"It was hard them looking back and seeing all the lights, something we wished we could have seen nearly [10] years ago. It has been good finally to get to this stage and maybe, just maybe, one day one of us may be lucky and also to have some justice for all of our men," said Tracey Keane-Harvey, whose son Riki was killed in the mine.

She said she would polish a piece of the mine's seal.

"And maybe make a trophy and send it to National," she said.

Bernie Monk said it was "pretty moving".

"The thing is I'm really happy for the families today, being at the coal-face like all of us have been," Monk said.

Asked what it was like to see the re-entry, he said this was the fifth time they'd had a go at it.

It wasn't until he saw the concrete removed that they were "on their way".

"We've got a long way to go," he said.

Pike River father Rowdy Durbridge, whose son Dan Herk was killed in the mine, described the re-entry as "almost like a mark of defiance" after Solid Energy sealed up the mine years ago.

"It was good. ..it's sort of a symbolism, if you like, of getting in. But to see the doors swing open was pretty good.

"I was part of the team that put the pillars in that hung on to the doors in order to give us an air lock on the first re-entry plan which was canned and Solid Energy in all their wisdom back-filled it and used it as a stopping.

"To me it's almost like a mark of defiance, you know, when you're told that you can't do something and you know in your heart that you can and thanks to the back-up that we've had, we've done it. We're in."

As for the mood of the families once re-entry had been made, Durbridge said it was like "going to a kid's birthday".

"I've been with the families over several meetings [over the years] and as you can well imagine .. there was a lot of tears, broken hearts, shattered people. But today, a complete turn around. It was like going to a kid's birthday.

"When you're told by professionals ... and they say it can happen and yet the people that are in position of a mine are saying it can't happen it's the most frustrating thing I have ever encountered, especially over the length of time of eight and a half years."

Families gather at the entrance to Pike River mine today. Photo / Supplied
Families gather at the entrance to Pike River mine today. Photo / Supplied

Sonya Rockhouse said to be able to stand there today and see the doors open "hit me in my heart".

"And to think, all this might never have happened if we hadn't blockaded the sealing of the drift and if New Zealand hadn't stood with us. It's just incredible."

Minister Responsible for Pike River Re-entry Andrew Little was proud to have fulfilled their promise of re-entering the mine.

"New Zealand is not a country where 29 people can die at work without real accountability. That is not who we are. And that is why today we have fulfilled our promise. Today we have returned.

"The tragedy that took these men's lives was the consequence of corporate and regulatory failure.

"Fulfilling the promise to do everything possible to safely re-enter is an act of justice for families who have waited for far too long.

"It is because of the families' tireless efforts that future mining tragedies might be prevented."

Little said there was still "much to do."

Families watch on as the loader goes into the Pike River Mine drift. Photo / Supplied
Families watch on as the loader goes into the Pike River Mine drift. Photo / Supplied

"We must find out what happened at Pike River. However long that takes, the recovery project will be done professionally.

"Most importantly, it will be done safely. Safety is the families' and the Government's bottom line. This was demonstrated when we delayed re-entry earlier this month.

"Today's milestone belongs to the families and to the memory of their men. It also belongs to all New Zealanders, who know that going home to your loved ones is the least you should expect after a day's work," he said.

Winston Peters said the re-entry was a "victory for the families who are fighting tirelessly for answers".

"Re-entry into Pike River is about justice. It's about finding out the truth, and it is about doing what's right for the families of those 29 men," the New Zealand First leader said.

"Today is a milestone for those families. The previous government showed so little courage and completely disregarded the need for accountability.

"We have shown today that going back in was possible and could be done safely," Peters said.

Canterbury University geology professor, David Bell, told Mike Hosking today that he doesn't think there's been any deterioration, because the mine was left in an inert state after being 90 per cent filled with methane.

He says just short of the rock fall there may well be some useful information about electrical circuits that may have triggered the explosion.

Grey District Mayor Tony Kokshoorn told Kate Hawkesby the Government's brief is to go to the rockfall at the end of a 2.3 kilometre tunnel.

He says 400 metres that hasn't been seen yet by robots or cameras will be covered, but there are probably no bodies in that area.

Kokshoorn says the Government can say it's done all it can for the families so they have to accept closure.