Drill breaks through at NZ mine as familes told to brace for worst

The fact that it still worked was "amazing" said police district commander Gary Knowles, the head of the search and rescue operation.

It suggested that if they had used their lights sparingly, the trapped miners might still be able to see, Pike River chief executive Peter Whittall added.

The helmet, found about 1km into the mine by a military robot sent down to investigate, belonged to Russell Smith, one of two men known to have survived Friday's blast, Whittall added.

However, the small piece of good news was tempered by new tests that showed air coming from a bore hole contained high levels of methane and carbon monoxide - but low levels of oxygen - inside the mine.

That means it is still too dangerous for rescue teams to enter the mine in Atarau, 47km northeast of Greymouth, on the western coast of New Zealand’s South Island.

"It is not safe to send rescue teams down at this time," said Knowles.

Some of the rescuers have said they are willing to enter the mine, but Whittall insisted it was too hazardous to let them.

It is hoped a camera and listening device can now be lowered into the main access tunnel.

The miners have not been heard from since the underground blast at about 3.30pm local time Friday. Two Australians, two Britons and a South African are among the group.

NZ Energy Minister Gerry Brownlee confirmed today that engineers have broken through with a 150mm bore hole.

"It had hot gas rushing up it and a lot of hot air as well,'' Mr Brownlee said.

"It will give a very good picture of what the gas state is in the mine and also the heat state. They are looking for a heat source.

"It is very significant information to the rescue planning,'' he told NewstalkZB.

It's believed a second robot also has been sent into the tunnel and another has arrived from Australia. Meanwhile, the families of the miners claim officials are keeping them away from the site.

Laurie Drew, whose 23-year-old son Zen is among those trapped, says relatives are beginning to get angry about the lack of information from officials.

"A lot of us family members want to be on site regardless of what way things turn out,'' Mr Drew told a small group of reporters this morning.

Police said safety concerns were stopping access to the remote mine on the west coast of the South Island.

Yesterday afternoon, family members were shown a sobering 52-second video of the effect of the powerful blast captured at the entry to the coal mine.

The hazy CCTV footage showed grey stone dust blowing out of the mine and a metal sheet violently flapping as the blast occurs at least 2.5km in to the shaft.

Pike River Coal CEO Peter Whittall told reporters families had not questioned why they haven't seen the footage earlier.

But Mr Drew disputed this.

"The video, they would have had it Friday night, they could have shown it to us Saturday morning,'' he said.

"(That would have saved) us that little bit of anguish we had gone through.

"You've got that information ... the family would have appreciated seeing things sooner.''

The parents of Josh Ufer, one of two Australians trapped in the mine, refused to comment to reporters.

Family of the second Australian Willy Joynson, 49, are also waiting in New Zealand for news.

New Zealand's prime minister has warned his nation to prepare for the worst, with no signs of life since the blast five days ago.

"We hope and pray that the missing men are alive and well," Prime Minister John Key said in a sombre address to parliament yesterday.

"But given we have not had contact with the men ... the situation remains grave. Although we must stay optimistic, police are now planning for the possible loss of life."

There were no signs of life in a refuge inside the Pike River coal mine when a camera  was sent down a 60cm shaft yesterday,  peeking into a pocket of fresh air where miners could retreat in an emergency.

The vision revealed some minor carnage, but nothing else, Pike River Coal CEO Peter Whittall said.

"There was no one there, there was no sign of any person in the area," he said.

There has been no communication with the men, aged from 17 to 62 years, since a methane blast ripped through the mine on Friday.

The police officer in charge of the rescue, Superintendent Gary Knowles, said anxiety was mounting as toxic gas levels continued to stop authorities from sending crews into the mountainside mine.

"We continue to plan for the rescue. However, we are aware that the likelihood of this occurring is diminishing and we have to be frank about the situation," Superintendent Knowles said yesterday.

"The risk of secondary explosion is real, and there's a great risk.

"We're not prepared to put other staff underground and put their lives in danger.

"The situation is bleak, it is grey."

New Zealand Police Commissioner Howard Broad said: "The situation is bleak and gets bleaker by the hour, by the day".

However, Mr Whittall said he was determined to remain optimistic.

"What sustains my hope ... is the survival or otherwise of a blast of that nature depends on where you are and what structure you're behind or where you're standing," he said yesterday.

"We still have a compressed air line going underground.

"I think it's becoming obvious that we may not be 29 guys all sitting together, waiting to be rescued.

"How many of them there are, I don't know. But those are the ones we need to rescue, and those are the ones I'm waiting to see."

Trapped Australians

Queenslander William Joynson and his wife, Kim, had spent a year in New Zealand and had begun packing to return to Queensland when Friday's explosion happened.

As soon as sons Jonathon, 13, and Benjamin, 10, finished the school year, the family planned to head home.

The Joynsons had shaped a life in New Zealand, focused on the coalmining community and the local Jehovah's Witness community, of which they were active members.

Mr Joynson is a "typical Australian", friends James Ashby and Rodger Griffiths said.

"He's big and strong and loud and funny - a typical Aussie," Mr Griffiths told the Herald Sun.

The other Australian Joshua Ufer, 25, has a pregnant girlfriend, Rachelle Weaver, waiting for him in Greymouth.

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