The Prime Minister and Governor-General will speak at a memorial for the 29 men who died in the Pike River Coal mine.

One of the miners who died at Pike River told a friend he feared for his safety in the month before last week's explosion.

"What gave armchair critics the right to criticise and worse - accuse the rescuers of deliberately sitting on their hands?"

The face of the country's worst mining disaster since 1914, Pike River CEO Peter Whittall, has fronted in the most trying of circumstances.

Experts suggest a split-second gas outburst may have overwhelmed the Pike River miners before they could respond to any alarms.

Jim Anderton seems to have made it his personal mission to end the life-and-death lottery that working in underground mines has entailed.

"We pray that their moment of fear becomes eternal peace," said Monsignor Gerry O'Connor during an emotional tribute to the Pike River miners in Greymouth.

There has been a third explosion at the Pike River mine this afternoon. The blast occurred at 3.39pm and lasted for 23 seconds.

A third robot that has gone 1575m into the Pike River coal mine has detected debris and destruction indicating Wednesday's blast was much more violent than the first one.

A Pike River Relief Fund Trust has been established for the families of the 29 men who died in the Pike River coal mine.

A small West Coast community will now face the task of recovering and rebuilding following a disaster of devastating proportions.

Liquid nitrogen could be used to stabilise the situation in the Pike River mine, experts told the Science Media Centre.

NZ is a nation in mourning as memorial services are held, condolence books arranged, and candles lit throughout the country.

He has to accept he has lost a son. But Marty Palmer won't give up until his son's body is back with the family so they can mourn properly.

The ACC will ensure money is the least of the worries for the families of the Pike River 29, says ACC Minister Nick Smith.