Mine safety experts will continue to monitor deadly gas levels through the night as 29 miners spend their third night trapped underground.
LATEST: It was thought noxious methane and carbon monoxide fumes were decreasing yesterday, however they are fluctuating.
A risk of explosion and high levels of gas mean it is too dangerous for rescue teams on the surface to go into the mine.
The miners, aged 17 to 62, are believed to be 2km in the depths of the mine.
Rescuers at the entrance to the Pike River coal mine are awaiting the green light to move in.
Gas level tests were being carried out every 30 minutes today.
An industrial drill was put into place tonight to bore 150m into the mine to allow further testing of the mine's atmosphere.
Specialist search and mine rescue staff along with other emergency services remain on site at the Pike coal mine tonight.
"This monitoring will allow first responders the earliest opportunity possible to judge when it is safe enough to allow teams to enter the mine and bring the men out," said Police Response Coordinator, Superintendent Kelvin Powell.
"This operation is a fine balancing act. We know families and friends are anxious to hear news of their loved ones and all response personnel are totally focused on bringing the men home."
SURVIVOR'S 'DISTRESSING' STORY
The first indication that something was wrong in the Pike River coal mine was when the gas monitoring devices in the mine were ''lost'', the company's chief says.
Meanwhile, the atmosphere in the mine, where 29 men have been trapped since an explosion on Friday afternoon, is potentially still explosive, New Zealand's mine rescue chief says.
Pike River chief executive Peter Whittall said he had spent two hours today with the two men - Russell Smith and Daniel Rockhouse - who walked out of the mine immediately after the blast.
Their experiences were traumatic, he said. But they could not add more detailed information about what happened on Friday.
Rockhouse's story was ''distressing", he added.
Whittall said the first indication that something was wrong was when the gas monitoring devices in the mine were ''lost'' but it was Rockhouse who had raised the alarm. He was initially overcome by the explosion but made it to the one working phone and raised the alarm.
He added that the surviving miners had seen no-one else in the mine. Initial reports on Friday suggested three other men were on their way up, but Whittall said these weren't correct.
He added that Rockhouse was 1.7km into the mine and did not see any evidence of collapse. The mine was ''very smoke filled'' he said.
"But that does not mean there hasn't been a collapse," Whittall said.
According to Whittall, Rockhouse walked out of the mine using breathing apparatus and was able to use a valve to get fresh air at each of the 50-100m outlets along the tunnel.
He wanted to get fresh air on his face. Smith was disoriented at first and Rockhouse helped him out. Rockhouse had found Smith on the ground but he was not unconscious.
Russell Smith was an hour late for work and was just driving a loader into the mine on Friday afternoon when the explosion hit.
"Because I wasn't as far up, the explosion wasn't that bad for me, (it) just bowled me over and knocked me unconscious and somebody dragged me 300m, pulled me around, and the two of us held each other to get out of the mine," he told TV3 News tonight.
He acknowledges he was "very lucky".
"(I) could have easily been blown to bits."
He said he saw a "flash" in front of him, then the blast hit him repeatedly.
"And it wasn't just a bang, finish, it just kept coming, kept coming, kept coming, so I crouched down as low as I could in the seat and tried to get behind this metal door, to stop getting pelted with all this debris. And my hat, belt, (it's) supposed to be hard to pull them off but everything was torn off me.
"(I) tried to get to my self-rescue (kit), but it was jammed that tight in the seat you can't get it out. And I remember struggling for breath. I thought at the time it was gas, but ... it was dust, stone dust, I just couldn't breath. And that's the last I remember," he said.
Whittall said his focus was on the families and there was ''real concern'' after spending most of the day with the families on their visit to the mine site today, adding he believed it was very worthwhile.
Whittall said there was a lot of emotion during the family visit today.
"It was very hard."
Things like miners' cars still parked at the mine were poignant, he said.
"They are waiting and watching," he said in referring to the families.
SITUATION POTENTIALLY EXPLOSIVE
"We're still in the gun barrel," NZ Mines Rescue manager Trevor Watts told gathered reporters in Greymouth. ''You put a bullet at one end of the gun it's going to come out the other end.''
"It's not like walking down to the local supermarket. The floor conditions are uneven. We can't just throw face masks on people and put them into the mine in a hurry."
He labelled the conditions the rescue team were working with "vast".
Watts confirmed one of the trapped miners belonged to the West Coast Mines Rescue Team.
"But… the whole lot of them are our brothers," he said.
Watts said any rescue attempts would be a staged entry.
''It's going to be safety first,'' he added.
"The gas readings are fluctuating".
He then added that small changes in barometric pressure had an effect on gas levels and that a worker taking a sample had to be evacuated yesterday.
"The teams have no idea of the temperature within the mine. They won't know until teams go into the mine."
Watts also signalled there may have been a fire since the explosion.
PM, HIGH COMMISSIONERS TO VISIT MINE
Prime Minister John Key will fly to the West Coast tomorrow morning with the Australian and British high commissioners as the Pike River mine crisis enters its fourth day.
Two Britons, an Australian and a South African are among the missing.
Mr Key said he would fly down by air force plane and either helicopter or drive to the mine site. He would return to Wellington later that morning.
SAFETY FIRST, SAYS RESCUE BOSS
Police Superintendent Gary Knowles, the Tasman Police District Commander, maintained it was still a rescue operation.
They are still working on the reduction of gases - and sampling every 30 minutes - but he reiterated he would not be sending rescuers down until it was safe.
''We have no idea how long it's going to take,'' Knowles said.
Whittall said he would not allow a "brave" volunteer down the mine even if they were prepared to risk their life. They could exacerbate the situation, he said.
Knowles added they would discuss releasing the names of the missing tomorrow morning.
''A lot of these people are grieving still,'' he said.
Watts said they were ''information gathering'' for gas and atmosphere analysis.
Some of the most highly respected experts in the world are now on site, including some from Australia, he said.
Watts confirmed there are six five-men rescue teams, doing eight-hour shifts each.
Many are local people supported by a team from Huntly. A seven-man team from NSW is ready to deploy in Christchurch, plus two senior officials from Australia.
There has been ''incredible'' support from within New Zealand, Watts said.
''We have more equipment than we know what to do with,'' he said.
Whittall said the drilling rig to give a second point of gas analysis was expected to start this afternoon or this evening.
Watts said a camera could fit down the bore hole.
Meanwhile Grey District Mayor Tony Kokshoorn said family members of the trapped men are starting to despair.
Family members today spent two hours at the site, as rescuers drilled into the mine.
Kokshoorn said anxiety levels among the families of the trapped miners were rising by the hour.
"People are starting to despair, its on their faces," he said.
However, he said the families were "really gratified, really pleased, in fact they were rapt" at being allowed to see the rescue operation.
It had allowed them to "understand the situation a little bit better" and had occupied their time.
He implored police to release the names of the men to end speculation in the community.
"It's not a secret and anyone could find out if they wanted to."
There has been no communication from any of the men since a gas explosion at the mine about 3.30pm on Friday.
Knowles reiterated this morning they were still focused on getting the men out.
The rescue mission remained hopeful, he said However, they were being realistic with the families and presenting them all of the options. He wanted to assure them ''everything humanly possible'' was being done.
"I am not going to put 16 guys underground and risk losing them to effect a half-arsed rescue."
The families understood sending men underground could ''cause a reaction we don't want''.
An international group of law officers had been set up to help the rescue mission, Knowles said.
He said a list of the missing men would be released ''in due course''. Police were contacting relatives around the world but they were still trying to ascertain all the nationalities.
Whittall had said this morning there was heating of ''some sort ''under ground - some combustion of material which was generating poisonous gases - still.
They didn't know what ventilation devices were still standing up, he said. The devices did not need power, he added.
However compressors were still blowing fresh air into the mine, he added.
A fan was put on site on Friday to blow fresh air into the mine but a decision was taken not to use it, Whittall said.
Asked what his best sense of where the men were, Whittall said: ''Look I just can't say.''
It's not an ''old deep'' mine he said, and the men were most likely where they were all deployed to. But he couldn't put an "X" on the map where each individual was.
Cameras weren't an option, because they couldn't push it 2km down a tunnel. A stepped shaft was also damaged.
While the explosion is not thought to have collapsed the mine, rescuers have been unable to enter due to dangerously high gas levels.
Laurie Drew, whose 21-year-old son Zen is among those missing, said families were becoming increasingly frustrated at the delay in attempting a rescue.
"If I had my way, I'd be down there and I'd go into the mine myself - I'm not scared or nothing - and I'd go and look myself, gas or not," he said.
"We go and sit there and listen to what they tell us in the office, listen to that, and it's just the same old runaround-runaround. Excuses for why things can't be done, instead of trying to find solutions."
Drew is one of the only family members to speak publicly so far. But he said they were also frustrated that they were not allowed onsite to either see their boys come out, or to hear whatever news there is.
"We want to be onsite so when they walk out, we'll be there."
"I just want my boy home."
As news filtered out that no rescue would begin overnight, churches and community halls in Greymouth and other parts of the West Coast filled with people, praying or just reflecting on the desperate plight of the miners and the long wait for their families.
Pike River Coal chairman John Dow said the delay was enormously frustrating.
"One of the toughest things is to not know enough to reassure people, and it is very difficult," he said.
"We can't approach the mine ... we can't go underground, because the underground conditions are judged by experts at the moment to be unsafe for the rescue people to go in," he said.
"One of the worst situations you can be in is not knowing what to say to people."
The Pike River Mine is on the opposite side of the Paparoa Ranges from the now closed Strongman State Mine where 19 miners died in an explosion in 1967. A total of 140 people are employed around the mine site.
The mine has been beset by delay, most particularly the collapse of an air ventilation shaft when it was close to opening for production.
The mine is the source of high grade coal used in steel production, most particularly for the Indian market.
Pike River Coal was listed on the New Zealand and Australian Stock Exchanges in July 2007 and has been in the NZX Top 50 listed companies since July 2008.
It has three major shareholders: cornerstone shareholder New Zealand Oil & Gas Limited (30 percent), and Indian customers Gujarat NRE Limited (7 percent) and Saurashtra World Holdings Private Limited (6 percent).
It now has almost 350 million shares on issue, currently held by more than 8000 shareholders, and a market capitalisation of NZ$400 million in mid-2009.