No attempt to rescue trapped miners tonight - police

Families wait for information about their loved ones as Pike River CEO Peter Whittall admits he's taking the disaster very personally.

There will be no attempt to rescue 29 miners trapped in the West Coast's Pike River Coal mine tonight.

Tasman District police area commander Superintendent Gary Knowles told One News the last sampling of mine quality air was taken at 4pm, with no further samplings until tomorrow morning.

It means a second night underground for the miners.

Mr Knowles said the mine air quality was still unsuitable for a rescue attempt.

Meanwhile, police have confirmed the nationalities of the 29 trapped workers.

There are 24 New Zealanders, two Australians, two British citizens and one South African.

The identities of three of the New Zealanders are known - Greymouth District councillor Milton Osborne, promising rugby league player Blair Sims and Ben Rockhouse, whose brother, Daniel, escaped after the blast.

Earlier, Prime Minister John Key said the relatives of the trapped miners were showing "signs of anxiety and genuine fear".

"I think that's natural in the situation they are facing," Mr Key said.

There was a growing sense of frustration amongst the group and he compared their predicament to the Chilean mining ordeal.

The families had to "hang on to hope", Mr Key said.

"The rescuers are brave people but they could make the situation worse by going in to the mine and igniting another explosion."

Mr Key said if it was a case of just going in and getting them out they
would do it.

"The issue is not about willingness, it's about practicality."

He said it was crucial that the families were given "absolute clarity of information".

Mr Key said he had received a huge number of expressions of concern internationally, including an email from Prince William.

He was heading back to Wellington tonight and would decide what to do from there.

Waiting for the go-ahead

There has been no contact with the miners since the explosion just before 4pm yesterday.

"We haven't heard a thing," Pike River Coal chief executive Peter Whittall told a press conference this afternoon.

Air samples being taken from the mine were being analysed for traces of methane, carbon monoxide, ethane and other trace gases throughout today.

They especially wanted to see lowering levels of carbon monoxide but Mr Whittall said the air samples had been inconclusive.

"The rescue teams need to see certain trends - they actually analyse quite a different number of gases within the air, not just one or two, and they look for a trending within certain gas ranges. They are not seeing that trend at the moment and therefore they cannot be conclusive as to what their strategy is," Mr Whittall said.

"They will typically be looking at the trend of methane, the trend of carbon monoxide, the trend of ethane, and a number of trace gases with the mine.

"In this case they are looking for a downward trend in carbon monoxide, with would indicate that there must be no further heating which would create a hazard underground."

Mr Knowles said rescuers wanted to go into the mine but could not until it was safe to do so.

"We are still waiting for a window of opportunity where we can do this. As the search commander I am not prepared to put people underground until we can prove it is a safe environment," he said.

"We still remain positive, and we believe that once that window of opportunity opens we are ready to go."

Rescue teams poised for action

Mr Knowles said the rescuers have been focusing on getting their equipment ready, going through drills and considering the various risks posed.

"When this window opens, we only have a short time frame to get in there, look at what's down there and make a decision on what we are going to do."

Mr Knowles said he was an "eternal optimist ... we're going to go down there and find those guys and bring them out".

However, he refused to be drawn on the chances the miners were safe, saying he did not work on gut feelings.

"These are people's lives. I'm not going to give a percentage to a family or work on my gut. We work on facts and when the time is right, and we are comfortable that it is safe, we'll be going in," Mr Knowles said.

"These are guys that are miners that are the experts. They're going in to save their colleagues."

When word comes that it is safe to go in, the rescuers will have to negotiate 2.5km of underground tunnels while carrying equipment.

"... we're currently scoping and looking at how do we get them in there quickly, where do we drop them off, what are the risks posed by putting them in now as opposed to waiting," he said.

Mr Knowles ruled out the possibility of dropping any supplies down the mine shaft to the men, as had happened for the 33 Chilean miners trapped underground for more than two months. All those men were successfully rescued.

"This is not Chile. It's a whole different type of mine," he said.

"We don't want to put something down there that causes a fire underground and risks those people's lives.

Mr Whittall said one of the advantages of Pike River was that it was a tunnel rather than a shaft mine and that meant rescuers could walk in and out of the pit.

There had been no indication that anything was wrong when the workers went into the mine at the start of their shift.

Air still flowing 'freely'

The explosion damaged a ventilation shaft but the mine had natural ventilation because of the layout.

The miners also carried breathing gear that would have lasted up to an hour on their belts.

Mr Whittall said the compressed air line, although damaged in the explosion, was still pumping fresh air into the mine and was "flowing very freely".

"We have kept those compressors going and we are pumping fresh air into the mine somewhere so it is quite conceivable there is a large number of men sitting around the end of that open pipe waiting and wondering why we are taking our time getting to them.

"We don't have any knowledge of what is going on underground because we don't have any communication."

Mr Whittall said if he was trapped underground near a fresh air pipe he would not move.

"I would be sitting tight. You would know you were in fresh air. You wouldn't know what the atmosphere was around the rest of the mine."

The families of the trapped miners had gathered at a Red Cross centre and were being kept fully informed of all developments, he said.

Miners discharged from hospital

An electrician who went into the mine soon after communications were lost yesterday found one worker lying on the ground. He recovered and walked out with minor injuries.

A second miner also walked out with relatively minor injuries.

Those men, Russell Smith, 50, and Daniel Rockhouse, 24, were working alone.

They were both discharged from Grey Base Hospital today.

West Coast District Health Board chief executive David Meates said the miners had requested privacy.

"They have been through a traumatic time and need to focus on supporting the families and friends of their colleagues. They ask that the media respect their wishes."