Andrew Little has defended the Government's plan to re-enter the Pike River mine despite the re-entry being unexpectedly delayed the day before.
Little, the Minister Responsible for Pike River Re-entry, announced on Thursday that "unexpected and unexplained" atmospheric readings had been reported in the mine, forcing operations to be suspended.
The Government announced in November last year that it planned to re-enter the site of the 2010 explosion after the former National-led government had deemed it too dangerous.
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National said the mine was too unsafe to re-enter and was prepared to seal it off, and faced criticism for not coming up with a re-entry plan sooner when it was possible all along.
But now that the re-entry has been delayed, Little has faced questions over whether the Government actually made the right decision.
When asked on Thursday if the former government was right in its decision not to re-enter the mine, Little responded with a strong "no".
Little said he saw the advice prepared for state-owned coal miner Solid Energy, the former owner of the mine, which in 2014 made the decision to not re-enter the mine due to safety concerns.
It said at the time that if rescuers re-entered there was a high chance more people would die. But later it was revealed that Worksafe had deemed re-entry feasible for a year.
"None of that advice said it wasn't possible to go in - it just said you had to take the right measures to mitigate the risks. It was always possible to do it," Little said.
"We had that advice, we've had the benefit of our own advice, including world-leading experts on underground mining and ventilation, and everybody has signed off on the plan of the project and approved the execution of it so far.
"We've come across this reading and it is enough for us to say, 'We can't explain it, we'll stop what we're doing until we can'."
Who's to blame for Pike River?
National MP and former Police Minister Judith Collins last year defended the former government's decision not to re-enter the mine, saying the advice the current Government had about re-entry was "certainly not the advice we had".
She pointed the blame at former Pike River Coal Ltd boss Peter Whittall, who she said should take the blame for the disaster which claimed the lives of 29 people.
A 2012 Royal Commission Report on the Pike River coal mine tragedy said the company's directors and executive managers paid insufficient attention to health and safety "and exposed the company's workers to unacceptable risk" in their drive to produce coal.
Whittall escaped charges under the Health and Safety Act when the Ministry of Business, Innovation and Employment (MBIE) allowed him to instead pay $3.41 million to the two survivors and families of men who died.
Little said on Thursday he had spoken with Anna Osborne from the Pike River Families Reference Group, who is the widow of Pike River victim Milton Osborne.
He acknowledged that the families "will be disappointed at another setback". But from the outset he said he made it clear that the safety of those re-entering the mine was top priority.
Little said he and Prime Minister Jacinda Ardern will join the families on the West Coast on Thursday night, and families will receive a comprehensive briefing from the agency on Friday.
He said the agency will know more after further testing and investigative work is completed over the next week, and a meeting of ventilation experts will then convene later in May.
The Pike River disaster has been contentious for years, with families of the victims blasting the police in September after an investigation was launched into whether they were responsible for a second explosion at the mine.