The 29 identification tags still hang on the board outside the mine. They're on the green side of the board, denoting the workers are 'in'. In the mine, somewhere deep inside, where they've lain for the last eight-and-a-half years.

Joanne Ufer stops and looks at her son Josh's ID tag. It gets her every time.

"It brings it all home … what's happened and that he's still here. When something like this happens I don't think you ever fully get over it," she says.

Ardern and Andrew Little join grieving families as they gather outside the entrance to the Pike River mine today for a ceremony despite the re-entry operation being delayed. Photo / Alan Gibson
Ardern and Andrew Little join grieving families as they gather outside the entrance to the Pike River mine today for a ceremony despite the re-entry operation being delayed. Photo / Alan Gibson

Her son Josh, a 25-year-old Australian drilling supervisor, died alongside 28 co-workers in the November 19, 2010 Pike River Mine disaster.

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Josh's fiancee, Rachelle Weaver, was 17 weeks pregnant when he was killed.

And his mother Joanne, who works in the mining industry in New South Wales, comes to Greymouth often to visit her granddaughter, born in May 2011.

She also makes the emotional pilgrimage up to the mine site to pay her respects to her son.

But this week felt different, coming over to witness the first steps back into the mine's drift to try to see if they can recover the lost men.

"Even leaving at the airport on Wednesday, I didn't realise how emotional I was going to be," Joanne said at the mine's entrance today.

"It was like coming back eight-and-a-half years ago when we were coming over. It was all unknown. And that's what it was like this week, all of the unknowns. What will happen when they get in there? How long will it take? What will they find?"

A small team of three expert miners were due to enter the coal mine this morning in the long-awaited bid to go back in.

Joanne Ufer, who lost family in the Pike River mine explosion, pictured outside the entrance to the Pike River mine. Photo / Alan Gibson
Joanne Ufer, who lost family in the Pike River mine explosion, pictured outside the entrance to the Pike River mine. Photo / Alan Gibson
Ardern speaks to staff who are working on the re-entry as they gather outside the entrance to the Pike River mine. Photo / Alan Gibson
Ardern speaks to staff who are working on the re-entry as they gather outside the entrance to the Pike River mine. Photo / Alan Gibson

But earlier on Wednesday, the Pike River Recovery Agency (PRRA) in charge of the re-entry operation got an "unknown reading of oxygen" from a borehole 2.3km into the mine's drift, where the roof collapsed in the 2010 explosions.

The oxygen had the potential for a "spontaneous combustion event".

The PRRA then took the decision to delay the re-entry on safety grounds.

It was a disappointing blow for the families – some, like Joanne who had travelled from afar for today's planned ceremonial event to witness the first steps back into the mine.

But they realised that the safety of the re-entry team was always going to be the number one priority.

Ross Harvey, whose 28-year-old son Riki Keane died in the tragedy, made the trip to the mine site from his home in Nelson.

Crown minister Andrew Little hugs a family member outside the entrance to the Pike River mine. Photo / Alan Gibson
Crown minister Andrew Little hugs a family member outside the entrance to the Pike River mine. Photo / Alan Gibson

He makes the pilgrimage every year to the site of his mining contractor son's death, and always finds it tough and emotional.

"We come down every anniversary [and] it's always hard, but now we see progress which is good," Harvey said.

"Today's been quite difficult, the whole week leading up to it, and then the news about they're not going to pull the seal out today, it's all very emotional."

Harvey supported the cautious approach and to put the safety of the re-entry team first.

"That's definitely what the families want," he said.

Prime Minister Jacinda Ardern sat beside Anna Osborne and Sonya Rockhouse – who both lost loved ones in the disaster - during the service.

It was Ardern's first trip to the mine site, and said today the focus was entirely on the families.

"They've been waiting a very long time to get to this point where the active re-entry has begun, is underway, and they've been fighting for that for a really long time. So for me, just seeing the huge amount of emotion around that for them is acknowledgement of the work they've put in and the sense of justice they feel now for that finally happening."