Police have confirmed a second explosion in the Pike River mine, where 29 miners are trapped.
Superintendent Gary Knowles emerged from briefing miners' families, saying it is his belief that nobody could have survived the blast, which occurred at 2.37pm.
Some of the miners' relatives ran from the briefing in tears, pushing through the cordon of waiting journalists, NZPA reported.
The operation to locate the miners is no longer search and rescue, it is a search and recovery mission, Mr Knowles said.
Mr Knowles, who was at the mine when it exploded, says telling the families was the most tragic thing he has ever had to deal with in his life. He then broke down in tears.
"We had to break the news to the family and they are extremely distraught,” he told reporters after the briefing.
"I was at the mine myself when the explosion occurred. The blast was horrific. Just as severe as the first blast - and we are now moving into a recovery mode."
Pike River Coal Mine chief executive Peter Whittall says he is unable to say for sure how the explosion occurred.
However, he said he is confident the explosion was not caused by the actions of the rescue team.
"If the men are no longer alive we still want them back, their families will want them back,” he said.
“But we can't go into an unsafe mine. It's just as unsafe as it was two hours ago."
Grey District Mayor Tony Kokshoorn said "this is the West Coast's darkest hour".
He described the news as sickening and said families were devastated.
"People were angry, shouting, some fell to the floor when they were told."
source: newshub archive