The families of some of the 29 men trapped in the Pike River mine expressed sorrow rather than anger at a meeting in Greymouth today, Prime Minister John Key says.

Mr Key met with the families at Greymouth's Civic Centre about midday, accompanied by Mining Minister Gerry Brownlee.

Afterwards, Mr Key told media: "There is an awful lot of sorrow in that room, but not anger. People realise that this has been a great tragedy.

"For now people are recognising the scale of the tragedy and that people around the world are offering their support."

He said the families deserved answers and that they would be delivered "in due course".

The Commission of Inquiry into the disaster would "leave no stone unturned," he said.

Earlier he said Cabinet would on Monday consider the terms of reference for the Commission of Inquiry.

Mr Key said he was not ruling out having an Australian mine specialist sitting on the three-person commission, which would also have a judge, and "wide-ranging powers" to subpoena people and gather all the information required.

Unstable environment

Mr Key said it was unlikely the bodies of the miners would be recovered in the short-term, due the instability of the mine environment.

"I don't think we are talking days, it will take longer than that."

Mr Key said there was a gas fire still burning in the mine but there was a risk of a coal fire breaking out.

"One of the things we are trying to do is to stabilise the environment so a coal fire does not take place," he said.

Mr Key said a number of techniques could be employed to try to allow rescue services to enter and recover the bodies of the miners.

He said he had received an offer from Australian Prime Minister Julia Gillard to send equipment to help.

"I can tell you we are enormous competitors with our friends in Australia when it comes to the sports field... but when a tragedy happens we all lock arms," he said.

"My utmost respect goes to the people of Australia for the utmost support they have shown New Zealanders."

Asked how it had been dealing with the tragedy as Prime Minister, Mr Key said it had been "a pretty torrid time".

But he added: "The reality is, whatever emotions I'm feeling pale in significance to what the families are feeling. If we can offer some comfort and support that's my role. I'm happy to step up and do that."

National service

Mr Key earlier told media that he would be working with Grey District Mayor Tony Kokshoorn on a memorial service to be held soon in Greymouth.

After meeting with the families, Mr Key said a national service planned for Christchurch in early December could be relocated to Greymouth if that was what people wanted.

He said no decision had been made on whether there would be a national day of mourning.

Mr Key thanked the police, rescue services and Mayor Kokshoorn for their work since Friday's blast at the mine.

He said the future of the Pike River mine remained uncertain.

"We don't know how long this issue will play out and what the future likelihood of the mine is," Mr Key said.