Flames were last night shooting from the top of a 108m ventilation shaft at the Pike River coal mine - and only a couple of mountain peaks away a 43-year-old fire from the Strongman mine continues to billow smoke.

The Royal Commission into the Pike River mine tragedy will be headed by High Court Judge Graham Panckhurst.

The Pike River Coal mine may have to be temporarily sealed after a fourth blast sent smoke and flames spewing from underground.

A royal commission of inquiry into the Pike River tragedy will look at causes of the blast and the initial response.

Families grieving after the Pike River disaster have called on a lawyer who rallied for victims in a previous West Coast disaster.

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.

"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.

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

Families of the dead men due to be bused to the Pike River mine tomorrow will still go, despite a third explosion at the mine this afternoon.

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