A file photo of the construction of a tunnel in the mine.

The entrance to the Pike River Coal mine where 29 workers were trapped after an explosion.

A Pike River Coal company vehicle sits at the closest safe point to the entrance of the mine where 29 workers were trapped inside after an explosion.

The police cordon near the Pike River Mine where miners are missing after an explosion.

REMOTE ROAD: A signboard of the access road leading to the Pike River mine where miners are trapped underground in Greymouth.

WAITING: Relatives of the miners and contractors trapped in the Pike River Mine leave a meeting after being briefed by mine management in Greymouth.

Blair Sims, making the tackle, has been named as one of those trapped in the mine.

John Key prepares to board an airforce plane to travel to Greymouth and the scene of the Pike River coal mine explosion.

Family members of the 29 miners and contractors go to a meeting with mine management.

Family members of the 29 miners and contractors after a meeting with mine management on Saturday morning.

Family members of the 29 miners and contractors after a meeting with mine management on Saturday morning.

Children at the Holy Trinity Anglican Church in Greymouth light candles for the trapped miners.

Churchgoers at a service for friends and family of the trapped miners, at the Holy Trinity Anglican Church in Greymouth.

A church service for friends and family to light a candle for the trapped miners, at the Holy Trinity Anglican Church in Greymouth.

The family and friends of the missing miners support each other while waiting for news.

The family and friends of the missing miners support each other while waiting for news.

The family and friends of the missing miners support each other while waiting for news.

The family and friends of the missing miners support each other while waiting for news.

The family and friends of the missing miners support each other while waiting for news.

The family and friends of the missing miners support each other while waiting for news.

The family and friends of the missing miners support each other while waiting for news.

The first Defence Force robot to be used in the mine rescue.

Relatives console each other after Tuesday morning's briefing, five days since the Pike River Coal mine explosion. At left is Martin Palmer, father of trapped miner Brendan Palmer.

Relatives console each other after Tuesday morning's briefing, five days since the Pike River Coal mine explosion. At right is Trevor O'Neill, brother of trapped miner Peter O'Neill.

Bernie Monk, the father of trapped miner Michael Monk, after the Tuesday morning briefing for relatives, five days after the explosion.

Left to right: Energy Minister Gerry Brownlee, Police Commissioner Howard Broad, and Police Minister Judith Collins at Greymouth on Tuesday.

An Air Force Iroquois drops off Search and Rescue crew working on the Pike River Coal mine rescue operation back in Greymouth on Tuesday.

Family leave a briefing after viewing CCTV footage of the explosion at the Pike River coal mine.

Family leave a briefing after viewing CCTV footage of the explosion at the Pike River coal mine.

The third robot was unloaded at Hokitika airport shortly after 8am.

The third robot, from Australia, arrived when two Defence Force robots were already in the mine.

A third robot arrived from Australia this morning on a New Zealand Airforce hercules.

Relatives leave their morning briefing on the Pike River Coal mine crisis at the Grey District Council buildings on Wednesday.

Relatives leave their morning briefing on the Pike River Coal mine crisis at the Grey District Council buildings on Wednesday.

Energy Minister Gerry Brownlee takes a phone call outside the press conference at the police station on Wednesday.

A local passes the miners hall in Runanga on the outskirts of Greymouth on Wednesday.

Police have said for the first time that lives could have been lost in the Pike River coal mine, where 29 miners haven't been heard of since an explosion on Friday afternoon.



"We still remain optimistic, we are still keeping an open mind, but we are planning for all outcomes and...also under this process we are planning for the possible loss of life as a result of what has occurred underground," Superintendent Gary Knowles told a press briefing at Greymouth this evening.



It was still too dangerous for a rescue team to enter the mine, because of the possibility of heating underground, he said.



"Gas analysis teams are now analysing the samples to determine if there is active fire or heating underground that may ignite. We have established a mine atmosphere sampling point where gas samples are being collected and analysed on a regular basis," Mr Knowles, the Tasman area police commander, said.



"We need to establish beyond reasonable doubt that an emission source does not exist. For this reason we in the process are establishing another sample point through another bore hole.



"I am going to reinforce the fact that we are doing this to ensure the safety of those miners underground and also the teams that have to go and rescue them."



Mr Knowles ruled out a rescue attempt being mounted today, saying the environment was still not safe enough and that he was not prepared to risk the lives of rescuers.



"It is dangerous to send mine rescue teams underground until we can establish it is a safe environment and thus we still continue to test on a half-hour basis," he said.



An army robot is being readied to send in to the mine but rescuers will not send anything in until they are sure sparks will not set off another explosion.



The robot will be capable of recording images but will also be equipped with simple things such as a rag tied to its arm; its movement will show air flow in the mine.



The army has been testing the robot throughout the day to ensure it can get far enough into the mine.



"They've been driving it up and down the road, they've got to simulate the 2.5km travel it's got to do," Pike River Coal chief executive Peter Whittall said.



The robot could go only as far as the air was clear, and would not carry any extra equipment such as supplies for anyone it might find along the way.



"The machine is designed to operate under its own weight and its own parameters. It's already going to be dragging up to 2.5km of cable behind it. It's only running on battery. The last thing we want to do is take all sorts of other things with it and get up 2km or 1.5km and go flat," he said.



"If it does that successfully then possibly it can go back up with other gas testing devices or other equipment on board."



A 15cm bore being drilled into the mine is nearing its target; it was down to 135m about 5pm but slowed considerably after that as it hit hard rock, as expected. A diamond drill bit would be used for the last 10m to avoid the risk of sparking.



"That will make it safer for us to drill that last portion through to the coal scene without it the risk of causing an ignition when it breaks through," Mr Whittall said.



"Once we do (break through), the collective wisdom on site is that the air will want to come up the borehole rather than down it so we'd expect that we'll start getting gas samples through that hole fairly quickly.



"Once that hole is open then we can start deploying a number of different techniques down the hole."



As well as taking gas samples out, a camera and listening device would be put in.

FATIGUE SETS IN

Fatigue has well and truly set in among rescue workers at the Pike River mine site on the fourth day of the disaster, with some working non-stop in an effort to get the 29 miners out.

1 of 21 JOSEPH RAY DUNBAR: 17, Greymouth. The youngest of the miners. The day of the explosion was his first day working underground. 2 of 21 JOHN LEONARD HALE: 45, Ruatapu. Lived in neighbouring house to partner Brenda Rackley on the outskirts of Hokitika. Hale was a contractor for Chris Yeats Builders. 3 of 21 SAMUEL PETER MACKIE: 26, Greymouth. 4 of 21 WILLIAM JOHN JOYNSON: 49, Dunollie, Australia. An experienced underground miner who worked for many years in the Burgowan mines at Howard, near Bundaberg. His wife and two children live in Queensland. 5 of 21 TERRY DAVID KITCHIN: 41, Rununga. Has three children under the age of 10. 6 of 21 ANDREW DAVID HURREN: 32, Hokitika. A keen hunter and fisherman, known as Huck to his friends. 7 of 21 DANIEL THOMAS HERK: 36, Runanga. Grew up between Greymouth and Hokitika and has done a lot of mine work, his grandfather says. 8 of 21 GLEN PETER CRUSE: 35, Cobden. Grew up in Greymouth. Leaves a partner and two children. 9 of 21 RIKI STEVE KEANE: 28, Greymouth. First five-eighth for the Blaketown Rugby Football Club, one of three club members to perish in the mine. 10 of 21 KEITH THOMAS VALLI: 62, Winton. The oldest of the 29 miners. 11 of 21 PETER O'NEILL: 55, Runanga. Member of a well known mining family and keen lawn bowler. 12 of 21 RICHARD BENNETT HOLLING: 41, Blackball. Grew up in Christchurch and is the first of his family to go down a mine. 13 of 21 DAVID MARK HOGGART: 33, Foxton. 14 of 21 JACOBUS ALBERTUS JONKER: 47, Cobden, South Africa. 15 of 21 STUART MUDGE: 31, Runanga. Orginally from Whangarei. His dad said working in the mine gave Stuart an "outlet for his energy". 16 of 21 MICHAEL MONK: 23, Greymouth. Rugby rep for the West Coast. Had a long-term girlfriend. Son of hotelier Bernie Monk and West Coast netball rep and coach Cath Monk. 17 of 21 JOSH UFER: 25, Middlemount, Queensland, Australia. Ufer's fiancee, Rachelle Weaver, is three months pregnant. 18 of 21 BEN ROCKHOUSE: 21, Greymouth. The younger brother of coal miner Daniel Rockhouse, 24, who was one of only two men to escape the mine. 19 of 21 CHRIS DUGGAN: 31, Greymouth. 20 of 21 PETE RODGER: 40, Greymouth. From Perth, Scotland, and lived in New Zealand with his girlfriend. 21 of 21 MALCOLM CAMPBELL: 25, Greymouth. Was due to marry Kiwi fiancee Amanda on December 18. Originally from St Andrews in Fife, Scotland.

Helipro chief executive Rick Lucas said his team, who had flown in the drilling rig, their equipment and supplies, were putting in some "very long days" but not as long as the drill workers themselves.

"Some of them are working 12 hour shifts. I was up there with them today and there's some pretty fatigued guys up there, they're giving it their guts for those boys," Lucas said

"But there's still an air of hope, that's what's driving everyone on."

JOHN COWIE/The Press Frayed nerves are snapping as the strain of the Pike River disaster takes its toll on the families of the 29 trapped miners.

Lucas said the atmosphere at the mine site itself was impossible to imagine unless you visited for yourself.

"I've worked in search and rescue for 25 years but never on anything as complex as this. They've got experts from everywhere. It's just so busy up there, everyone's giving in 110 per cent."

He said there were "endless food and drinks" for the workers, and the helicopters had brought in portable huts so the drill workers could stay close to the site.

The pilots were staying and Greymouth and would be there until the rescue was complete.

"We're here until the end. We've got four machines and back-up pilots," he said.

"We're just getting on with it like everyone else."

INQUIRY 'ALMOST CERTAIN'

A Commission of Inquiry in to the Pike River coalmine tragedy appears almost certain.

Prime Minister John Key this afternoon returned to Wellington for a Cabinet meeting after a second visit to the Pike River coalmine, near Greymouth, this morning.

Key told reporters the explosion at the mine was "very unusual".

He appeared to suggest that a commission of inquiry would unfold after the crisis was over. He said he did not want to speculate on what structure a commission of inquiry would take.

However, a Royal Commission of Inquiry was typically for social issues and a commission of inquiry had been set up after the Cave Creek tragedy.

"It is a highly, highly irregular event that has taken place and we'll need to understand what the cause of that is," he said.

"There will be an inquiry, if not inquiries in to what has taken place at Pike River."

"I don't want to speculate on the nature of those inquiries, nor what they may or may not find. We need to understand better what's gone on and why and in due course, we'll seek to find those answers."

Key said Energy and Resources Minister Gerry Brownlee would stay in Greymouth for the time being. Labour Minister Kate Wilkinson had briefed Cabinet today and would also probably go back to Greymouth soon.

Key has no immediate plans to return to Greymouth but said his plans were "fluid".

"I certainly don't want to get in the way of rescue efforts but I also want to show that the Government takes this issue very seriously and every possible resource is available to aid the rescue."

HI-TECH RESPONSE

A specially-adapted NZ Defence Force robot will be sent into the mine, which is full of toxic fumes, to see if there are any signs of the men, who have been entombed since Friday.

A camera will be attached to the robot, which will also detect levels of dangerous methane and carbon dioxide gases which have flooded the colliery. The fumes are preventing rescue teams from entering.

It will be sent 2km deep into the horizontally-dug mine to where the men are believed to be. They haven't been heard from since a large explosion shortly before 4pm on Friday.

The drilling of a 162m-deep bore hole will also continue today. Once specialists reach the seam, at around 150m, they will switch to a diamond-tipped drill bit to prevent igniting sparks, which could set off another devastating explosion.

Once the drill breaks through into the mine, rescuers will look at lowering in another camera. It will also allow more samples of the deadly gases to be tested.

Airforce and defence helicopters are on standby with night vision equipment should the mission stretch into darkness. And a path is being cut out of the rugged mountainside to cut down on helicopter time bringing gas samples back and forth.

The specialists are also looking at using seismic gear to listen for any signs of life below ground.

Whittall said the drilling was going ''very, very well.'' As of 7am they had reached 100m, he said.

''We've had a lot done overnight. The guys who have been doing the drilling have done a phenomenal job. They have mobilised the drill unit, they were still flying it in when we were up there with the families yesterday.''

Once the rock is hulled through, it will provide ''a number of opportunities,'' he said, ''provided it's in the right spot and it's everything we hope it will be.

"We've got opportunities to sample gas from that point because at the moment we've only got the one gas sampling point.''

Putting laser imaging equipment and cameras down the hole - around 15cm in diameter - will allow the team to gather ''a vast amount'' of new data, he said.

This could be to within centimetre-sized rocks sitting on the ground.

''It will create a proper image of what's down there.''

He also revealed there is a second, existing, bore hole dug above the tunnel. Samples can be taken from there but the air at that point is likely to be fresh, he said.

Equipment to lay a special pipeline into the mine is being flown in from Queensland.

The tube bundle line, which is about 10mm, will have a pump attached to it and will take gas from the chamber and feed it into the ''amenities'' area, where all the sampling gear is sited. This will cut down on the need for taking bag samples every 30 minutes.

''We can actually real-time monitor what's going underground so that's a great advance. That gear is coming out of Queensland. It's not typically used in New Zealand.''

Mr Whittall said it was very hard for him to listen to the list of his missing men read out to media. He was focused on bringing them home safe.

More relatives were taken to the mine site this morning and Whittall was to show them around the site. They would also talked to rescue coordinators about the operation.

Before journalists - who have flocked to Greymouth from all over the world - were briefed, relatives gathered at the district council building to be updated by the men heading the mercy mission.

Earlier Mr Key said these were testing and difficult times. But he said it was owed to the men to carry out the rescue in a way that doesn't endanger their lives.

He said US President Barack Obama had been in touch to offer support along with a number of world leaders.

He also visited the site this morning.

Knowles said the mine rescue teams were still on standby. ''They are looking at which sections they will enter first.''

He said: ''Given we have not had contact from the men for three days, every effort is being made to carry out a rescue and we will go from there.''

FAMILIES 'NEED' RESCUE TO START

Earlier, Grey District mayor Tony Kokshoorn said a search and rescue effort to save the trapped Pike River miners needed to go ahead today for the sake of their families.

"Somehow today they have to make a move forward. But even as I'm saying that I'm thinking, I don't know how, I just don't know how."

"We're in limbo, we're desperate. [Families are] reaching the end of their tethers," Kokshoorn said.

"Every hour and every day that goes by we have to face the facts that they can't stay down there indefinitely.

"Those families need to hear from the police that there is some movement forward."

The weather in Greymouth was fine today, he said.

"That may be a good omen for us. I'm just hoping for a big step forward. But then, I don't know what that step is. But this can't go on, it's too hard on the families."

"The only way they'll start is with a reduction in gas levels. And that's going to be hard."

Kokshoorn earlier said anxiety was rising by the hour. "People are starting to despair, it's on their faces."

FAMILIES MEET POLICE, COMPANY

Families of the 29 trapped miners were hugged by police officers as they arrived at a meeting to update them on the rescue mission this morning.

The relatives travelled to the local council offices in Greymouth to hear the latest details of the police-led mercy mission.

Afterwards, family members stood outside with a policewoman looking at a detailed map of the mine interior.

Survivor Daniel Rockhouse, 24, was among the group of relatives.

His brother Ben is one of the missing. Rockhouse walked out of the mine on Friday after the blast with colleague Russell Smith.

Rockhouse, an electrician, exchanged long hugs with some of the waiting women.

THOUGHTS AND SYMPATHIES

The Board and staff of Pike River part-owner New Zealand Oil & Gas have extended their "thoughts and sympathies to the men trapped at the Pike River Coal mine, their families, friends and colleagues".

"Like all New Zealanders, we are hoping for the best possible outcome from the rescue and recovery mission," NZOG said in a statement to the Stock Exchange this morning.

NZOG, which holds just under 30 per cent of Pike's shares, said it would make "further statements on market-related issues" but did not indicate when.

Pike River shares were suspended from trading on the ASX late on Friday till Tuesday morning, pending a further announcement. After news of the mine explosion, Pike shares dropped 14 per cent in Australia, before the shares were put in a trading halt.

NZOG also asked for an immediate trading halt till Tuesday.

NZOG has had a long and close association with the Pike River coal mine. The project was developed by NZOG over two decades before Pike River Coal was publicly floated in 2007, and NZOG holds a 29.4 per cent stake in Pike River.