No one was hurt in the latest explosion at the Pike River colliery, the mine company's chairman said. At the time, emergency crews had gathered away from the mine entrance for a ceremony to mark one week since the first blast.
"It happened at 3:39 pm (0239 GMT) and lasted about 20 seconds," Pike River Coal chairman John Dow told reporters. "As far as we can tell from the CCTV footage, it was smaller than the two explosions than we've had already."
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In a chilling coincidence, the initial blast that trapped 29 miners at the pit in the remote west coast of New Zealand's South Island hit just five minutes later on the previous Friday.
"The blast occurred as emergency services' representatives gathered at the mine site," police said.
"The group was some kilometres (miles) away from the mine portal at the time and not in any danger."
In Greymouth, about 50 kilometres (31 miles) from the mine, locals were unaware of the drama at the pit and with the minute's silence marking the first blast, which caused the country's worst mining disaster in almost a century.
"It's been such a long week, it seems to have gone on forever," hairdresser Nacayla Bryan told AFP.
"It's the saddest thing that's happened in my lifetime," the 20-year-old added.
The week was an emotional rollercoaster for the miners' families -- beginning with hopes they were trapped but alive underground, then turning to anger among some relatives as rescuers refused to enter the mine due to danger from toxic gases.
A second explosion Wednesday prompted authorities to say no one could have survived, creating a wave of grief as Prime Minister John Key said the whole nation had been plunged into mourning.
Dow said Friday's blast would not affect plans to retrieve the bodies of the miners -- 24 New Zealanders, two Australians, two Britons and a South African -- entombed in the mine, which remains flooded with explosive methane gas.
"It won't be a setback at all, we've consistently said that this has been a potentially explosive environment right from the beginning... we've known that all along, so it won't make any difference," he said.
The latest explosion would not stop plans to bus up to 500 relatives of the victims, some of whom have travelled from overseas, to the mine on Saturday to help their grieving process.
But it may be a blow to the company's hopes of reopening the colliery once the miners' bodies had been removed and the area rendered safe.
Even before Friday's explosion, Dow conceded there were doubts about the pit's future because the cause of the gas blasts remained unknown.
"When you've got the uncertainty we've got at the moment, not knowing what you're going to find, then you'd have to draw that conclusion now," Dow said said shortly before the third blast.
He said expressions of sorrow from dignitaries including Britain's Queen Elizabeth II -- who is also New Zealand's head of state -- US Secretary of State Hillary Clinton and Pope Benedict XVI had buoyed the community.
"It's been very helpful and uplifting for Pike, for the staff, for the board to know that around the world there's such an outpouring of public goodwill and sympathy and condolence," the mining executive said.
To assist the grim task of recovering bodies from the mine, a specialist jet engine, known as a "gag unit", was flown in from Australia to try to make it safe for emergency crews to enter.
The device would use water vapour and gases to purge oxygen from the mine and ensure there were no more explosions, the machine's operators said.
The machine could not have been used while there was a faint chance some of the men remained alive in the mine shaft at Pike River,
Grey District mayor Tony Kokshoorn said recovering the victims was an essential part of bringing closure to distraught relatives.
"We want the miners out of the mines and into the loving arms of the families," he said.
