A 3News cameraman reportedly said the flames reached this height on the surface after travelling 160m up the shaft.

Pike chief Peter Whittall said the ventilation shaft was acting like a chimney, according to the New Zealand television network.

He hoped the coal fuelling the fire was shaken up from previous explosions at the mine and did not indicate the mine’s Brunner seam, up to 9m thick with a premium coking coal grade, was alight.

The Queensland Mines Rescue Services’ GAG inertisation unit is ready to start up tonight, according to the New Zealand Herald.

Basically a jet engine, the unit will overwhelm any fires and explosive gases underground with nitrogen, carbon dioxide and water vapour.

But management is also reportedly considering sealing the mine from the surface to starve the underground fire of oxygen.

The massive fire is likely to destroy evidence underground and stymie investigation efforts.

NZ Prime Minister John Key is seeking cabinet approval for a Royal Commission of Inquiry into the mining disaster which has cost 29 lives.

The terms of reference for the inquiry are still being finalised.