Rescuers were late yesterday waiting for the green light to mount a search for 29 miners trapped by an explosion at a mine in New Zealand as fears of another blast held them back.

There were 29 miners still unaccounted for following an underground mine explosion in New Zealand, Pike River mine chief executive Peter Whittall said.

The operators of the Pike River coal mine near Greymouth on the South Island’s West Coast held out hope the missing men were alive.

Pike River chairman John Dow told reporters it was possible the miners reached a safety refuge where there could be fresh air.

However, there was no communication with the missing miners and the ventilation system was not working at the mine located in an isolated area about 50 kilometres north of Greymouth.

Search and rescue workers gathered at the scene preparing to enter the mine when given the go ahead, although police said the air quality would be fully tested before a rescue mission could be mounted, with fears a gas build up could cause another explosion.

Two miners who survived the explosion just before 4 p.m. yesterday were being treated in hospital for minor injuries. They indicated three others were making their way out they had not appeared by daybreak yesterday.

Grey District mayor Tony Kokshoorn said the rescue was difficult and could take days. But he said the experience of Chile’s miners, who were successfully brought to the surface last month after surviving more than two months in a tunnel below the Atacama desert, was a source of inspiration.

“We are holding on to hope. Look at Chile, all those miners were trapped and they all came out alive,” he told Fairfax Media yesterday.

Pike River Coal chief executive Peter Whittall said the miners were about 120 metres beneath the surface.