The New Zealand mine drama went into its fourth day Monday with still no word of when a bid to rescue 29 men trapped after an underground explosion will be made.

Rescue teams of miners remain on round-the-clock standby at the Pike River coal mine awaiting approval that it is safe to go in to try to rescue those trapped in Friday?s accident.

Authorities say an attempt cannot be mounted while dangerous levels of toxic gases continue to pose the threat of sparking another explosion that would endanger rescuers in the mine on the west coast of the South Island.

Drilling of a bore hole through about 150 metres of rock to allow different samples of air to be taken and a microphone lowered to listen for sounds of life in the mine was reported to be about halfway completed early Monday morning.

Nothing has been heard from the missing men, who are aged 17 to 62, since Friday afternoon?s explosion. They are 24 New Zealanders, two Australians, two British citizens and one South African.

Their names have not been released officially, but many have been identified in media reports.

Company officials and police were scheduled to brief distraught relatives, who increasingly fear the worst as each day passes, on the rescue plan Monday morning.

Some family members were taken in buses from the west coast?s main town, Greymouth, where they have gathered, to the mine site, 50 km away, Sunday to talk to the rescue parties.

Two miners who were the only known survivors of the explosion have told their stories to local media for the first time.

?I thought I was dead,? Daniel Rockhouse, 24, who was blown off his feet while refuelling his loader in a part of the mine away from the coalface where the rest of the miners worked, told the New Zealand Herald.

?All I could think about was seeing my wife and kids again.?

Fighting a deadly buildup of carbon monoxide as he tried to escape, he found fellow miner Russell Smith, 50, collapsed on the ground.

?He was away with the fairies,? he said. As he dragged Smith to safety, they were able to breathe some fresh air from compressed air lines along the way.

As Smith?s condition improved, Rockhouse helped him to his feet. ?I put my arm around his shoulders and held on to him as hard as I could, and we hobbled for the next kilometre.

?All the way down I was saying to Russell, ?We?re gonna make this, mate. Think about your wife, think about your kid ?? I know I am??

Smith told TV3, ?I just remember seeing a flash of something in front of me and then the concussion hit me. It wasn?t just a bang. It just kept coming, kept coming, kept coming.?

He said he crouched down as low as he could in the loader he was driving to stop being pelted with debris. ?I just couldn?t breathe and that?s the last I could remember and then someone found me about 15 minutes or so later.?

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