While initial progress was swift, drilling hit a section of hard rock around the 135m mark.

A diamond core drill bit must also be used in the final metres to prevent sparking.

The 15cm diameter hole will intercept a roadway roughly halfway between the mine’s pit bottom and the working areas where many of the missing miners are expected to be.

Pike has also secured fibre-optic cable to put down the hole to get first images underground since the Friday afternoon explosion.

Toxic and flammable gas readings remain too high for rescuers to safely enter the mine.

Pike has released a schematic of where the explosion was expected to be in the mine.

Daniel Rockhouse

The fate of the 29 missing miners appears grim after survivor Daniel Rockhouse shared his story with the New Zealand Herald.

He started afternoon shift as the bolter on the ABM 20 bolter miner but reportedly left the face on a loader to refuel it about halfway into the mine.

A white light flashed down the main roadway and the associated blast threw him off the machine and knocked his head into the rock wall.

"I got up and there was thick white smoke everywhere – worse than a fire,” he told the newspaper.

“I knew straight away that it was carbon monoxide."

He donned his self-contained self-rescuer but reportedly first ran into a dead end of the mine out of panic.

He later collapsed in the main roadway but, after recovering consciousness, managed to get to a compressed air line to gain fresh air according to the report.

Rockhouse reportedly felt “drunk” from carbon monoxide poisoning but managed to not only phone the mine manager but also dragged out and helped an unresponsive sparky, Russell Smith, make it to a fresh air base in the mine.

Using the compressed air lines in the mine both of them later made the rest of the 1km journey out of the mine.

In a separate report, Smith told the newspaper he was dragged about 300m and he was lucky he arrived at work an hour late or he would have been deeper in the mine.

“It wasn't just a bang,” he told the New Zealand Herald.

“It just kept coming, kept coming, kept coming.”

He reportedly remembered being “pelted with all this debris” and not being able to breathe before Rockhouse helped him about 15 minutes later.

Rockhouse’s brother Ben is one of the 29 miners who remain missing after the underground explosion.