Workers are back cutting into the concrete seal plugging the Pike River Mine drift after the leaky tubes that delayed the long-awaited re-entry were replaced.
Expert miners were due to enter the West Coast mine on May 3 to start an operation trying to recover the 29 men killed during the November 19, 2010 disaster.
The Pike River Recovery Agency (PRRA) had been working for months to purge methane and oxygen from the mine by pumping in nitrogen through pipes before they headed underground.
But the day before they were due to go in, they 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".
Pike River Recovery Agency chief operating officer Dinghy Pattinson denied it was a tough call to delay the re-entry, because they have also stressed a safety-first attitude.
They soon discovered a leaky sampling tube was to blame for the oxygen spike.
But now that the tubes have been replaced and tested, work on cutting into the concrete seal has resumed.
Pattinson confirmed to the Herald today: "Integrity testing has been completed on all the monitoring tubes that check the mine's atmosphere. The concrete cutting is under way, along with other preparations for re-entry."
Anna Osborne, chairwoman for the Pike River Family Reference Group and whose husband Milton died in the tragedy, posted on the 'Supporting the recovery of our Pike 29' Facebook page that work was going well.
"The concrete cutting is under way, and the drillers are making good progress," she said.
"The atmosphere in the drift is good. No date has been set yet for the re-entry but it certainly won't be too far away."
At the time of the delay, Osborne admitted being "slightly" disappointed but was glad that the agency was putting the health and safety of the men going back into the mine first.
It wasn't a showstopper, she said, and once the issues are investigated, "it will be back on".
A ceremonial event was still held at the mine's entrance on May 3, attended by Prime Minister Jacinda Ardern.
Ardern sat beside Osborne and Sonya Rockhouse during the service and said 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 under way, 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."