"Unfortunately I have to inform the public of New Zealand at 2.37pm today there was another massive explosion underground and based on that explosion no one would have survived," the New Zealand Herald
quoted Police Superintendent Gary Knowles, who headed the rescue operation, as saying.
He was at the mine when the blast, which lasted 30 seconds and was stronger than the first one, took place.
"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," TVNZ
quoted Prime Minister John Key as saying.
He said there would be inquiries, as well as memorial services in Greymouth and at a national level.
Rescuers had thought they might enter the mine during the afternoon, but there were suggestions that it was not safe.
David Bell, from Canterbury University, said the explosion would have been caused by a mix of gas which became unstable.
Pike River Coal chief executive Peter Whittall said drilling broke through into the mine tunnel earlier in the day and found the air was high in carbon monoxide and methane, and very low in oxygen.
Camera images were black and grainy.
Mining expert David Feickert told TVNZ
it was likely that anyone still alive had become unconscious from carbon before the second explosion and would not have felt the blast.
It is expected that the mine will be flooded with carbon dioxide to clear oxygen and extinguish any fires before bodies can be retrieved.
Some family members are angry that a recovery operation did not take place soon after the first explosion, before gases built up underground