Australia is sending a team of rescue experts to New Zealand to assist frantic efforts to save 29 trapped miners, its Foreign Minister Kevin Rudd says.

A technical expert from Emergency Management Australia and a team of six mine rescue experts from New South Wales Emergency Management would leave Australia today to lend their assistance to the rescue operation at the Pike River Coal mine near Greymouth, Mr Rudd told reporters in Sydney.

"These forms of assistance will be deployed today and other forms of assistance remain ready for deployment should that be necessary," he said.

Twenty-nine miners, including at least two Australians, have been trapped in the mine since an explosion on Friday afternoon.

The decision to send the team was made following a conversation with the New Zealand minister for mines this morning, Mr Rudd said.

A team of 12 mine rescue experts from Queensland remain on standby should the New Zealand Government need them, he added.

The government did not yet know if more than two Australians were trapped and was "gravely concerned" for the miners' wellbeing.

"We still have uncertainty about the precise number of Australians who may be directly involved in this," he said.

"We are working our way through the company employment lists, the mine manifest and other details as they're available to us."

No details about the Australian miners would be released at this time, Mr Rudd said.

The Australian consul general has gone to the mine site and will be joined by supplementary consulate staff, "in order to work with friends, families, loved ones", Mr Rudd said.

"We intend to remain in the closest possible contact with our New Zealand friends on this unfolding situation at the mine explosion site.

"The Kiwis are our mates across the Tasman, this is a really difficult situation.

"What mates do is we help when things go wrong and that's what Australia is doing and we'll be there to support our Kiwi friends in a very difficult hour."

- AAP