Pike River coal mine has been rocked by a second, massive explosion and there are no survivors, police have said.
Superintendent Gary Knowles said there was no chance that any of the 29 miners missing since Friday's first explosion survived the second blast at 2.37pm this afternoon.
Today's blast lasted 30 seconds and was more significant and stronger than the first explosion.
Grey District Mayor Tony Kokshoorn said it was "the West Coast's darkest hour, it doesn't get worse than this" and Prime Minister John Key said it was a national tragedy .
"The 29 men whose names and faces we have all come to know, will never walk amongst us again. We are a nation in mourning," Key said.
Tough there is now no hope of rescuing any of the miners alive, Pike River CEO Peter Whittall said: "We have still got to get our boys back. We are going to get everyone we can."
Knowles announced late this afternoon: "Unfortunately I have to inform the public of New Zealand that at 2.37pm today there was another massive explosion underground and based on that explosion no one survived.
"This is one of the most tragic things I have had to do as a police officer.
"I was at the mine myself when this actually occurred and the blast was horrific, just as severe as the first blast and we're currently now moving into recovery phase."
Key said: "To lose this many brothers at once is an agonising blow."
He offered his condolences to Australia, South Africa and the United Kingdom, who all lost miners in the disaster.
Key praised all those involved involved in the rescue team though the nature of the mine prevented them entering. "They didn't go into the mine because it was unsafe to do so."
He said inquiries would follow as would memorial services in Greymouth and at a national level, possibly in Christchurch.
Police Commissioner Howard Broad defended the way the thwarted rescue was handled. "This was an extremely professional and thoroughly detailed operation," he said.
'Looked for hope'
Whittall said he delivered the news to the families himself.
He said: "It was hard, obviously. They have looked to me for hope and for keeping them informed. I have tried to do that as factually as I can. It was my task and I wanted to tell the families."
Rescuers had been preparing to possibly go into the mine this afternoon, but information suggested it wasn't safe. Shortly afterwards the second explosion happened.
Whittall said it was similar to Friday's explosion, but added: "It was more significant, it was larger, it was stronger, it lasted about 30 seconds."
He said: "It will probably be unlikely there will be any survivors from that. It was probably unrealistic that many of them would have come out alive anyway."
There was no possibility that any rescue work caused the explosion. No one was injured outside the mine.
As he left the room after making a brief statement to cameras he received a round of applause from people present including media and Energy Minister Gerry Brownlee.
David Bell from Canterbury University said the cause of the explosion would have been that the mix of gas would have become unstable and this was why the rescuers had been unable to go into the mine.
Kokshoorn said families broke down when told and there was anger directed at the police but not at Whittall.
He said rescue workers were sent in straight away, which was "ironic", but Whittall later dismissed that and said no rescue teams have gone into the mine.
Kokshoorn said he understood the cause of the explosion was the build up of gases over the past five days.
Grieving families left the afternoon briefing at Grey District Council and did not want to talk to the waiting media. An ambulance arrived to offer assistance to the family members.
Lawrie Drew, father of Zen Drew, 21, later spoke to cameras. He was clearly angry but said: "I am still hoping that somebody can be found that is still alive."
Reverend Tim Mora, who was at the briefing, said the families were "utterly devastated".
Mining expert David Feickert told TVNZ it was likely the men became unconscious from carbon monoxide prior to the second explosion and so would not have felt the blast.
ONE News presenter Peter Williams at the scene said the first member of the public he saw after the announcement was "ashen faced".
Earlier today Knowles said initial samples of gas that escaped from a bore-hole drilled this morning showed high levels of toxic gases. He warned they might never reach zero.
He added at a media conference this morning: "It is a very unstable environment and currently it is not safe to go underground. It may never reach that point, but if it does, rest assured we are ready."
Pike River Coal chief executive Peter Whittall said drilling broke through into the mine tunnel this morning, and the first samples showed the air was high in carbon monoxide and methane. He said it was also very low in oxygen.
He said then that it was not appropriate to send rescue teams underground at that time.
A camera put down the bore hole sent back images which are black and grainy.
A second army robot had gone into the mine.
The first robot sent into the entrance tunnel has found a helmet belonging to injured loader driver Russell Smith.
The light on the helmet is still going almost six days after the explosion.
Grey District mayor Tony Kokshoorn said this morning that families and the West Coast community were hanging on to hope despite the grim situation for their loved ones.
"We know we are losing hope now, but unless someone shows us otherwise, we are hanging on to all hope," he said at the time.
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