Police Commissioner Howard Broad summed up the feeling about the 29 trapped Pike River miners, in a press conference tonight, saying: "This is an extremely dangerous situation, I can't stress that enough.

"The situation gets bleaker by the hour, by the day."

But Pike River CEO Peter Whittall said he still held out hope there were survivors in the mine.

"I think it's becoming obvious there's not 29 guys sitting together waiting to be rescued," Mr Whittall said.

"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."

He also said a camera had today been lowered down a slimline shaft into a fresh air base, an area that would be used by miners in an emergency. The camera showed minor damage and "general disrepair."

Mr Whittall said there was no evidence any miner had entered the area since the blast.

CCTV blast footage revealed

The news came as those present were shown a video of Friday's explosion.

Pike River CEO Peter Whittall said CCTV footage shows the blast was a "strong symbol" and "was large and went on for a long time."

Mr Whittall also pointed out that footage showed the mine entrance was at the further most point from the blast.

However, he emphasised that two men survived the explosion and this is what gives him hope.

"What's sustaining my hope is the information we've had from day one, that survival of a blast of that nature depends on where you're standing. Daniel was only a couple of meters off the road and not in the direct path and got up," he said.

Drilling the last 10 metres

Mr Whittall said the drilling of a bore hole into the mine is still 10 metres from completion, and would be finished in four to five hours.

He said officials were preparing to start drilling on a second hole, closer to where many of the miners were likely to be located.

"The second drill site's being prepared. As soon as we finish the first they'll start stripping the rig down and start moving it to the next site by helicopter - which is only a few hundred metres away," Mr Whittall said.

Second robot arrives

Earlier, a second New Zealand Defence Force robot arrived at the mine, after the first robot malfunctioned last night when water fell on it, Defence Minister Wayne Mapp said today.

"As you know the (first) robot failed 550 metres into the mine. The robot is not actually designed for this purpose but can operate in rain but this instance was effectively hit by a waterfall, which then knocked it out."

A spokesperson for Wayne Mapp said "it will be up to the people on the ground" to make the call on whether to send the second robot into the mine.

The robot was designed for 'mine disposal' and, if used, would be adapted to travel the two kilometres into the mine.

"They'll put extra batteries on them...they've put gas detection equipment on them and they already have two cameras".

The robot was not designed for mine-like conditions, Mr Mapp said.

Meanwhile, specialists mine rescue vehicles were also being flown on from the United States.

"My understanding is that those will be brought in by civil aircraft - the role of the aircraft is to bring them directly to Greymouth."

Grey District Mayor Tony Kokshoorn said the breakdown of the robot had angered family members and made them question the rescue efforts at Pike River.

Mr Mapp said he expected 'lessons would be learned' from this morning's breakdown, but the truth was 'they are not designed for this purpose'.

"They weren't expecting this level of water in the mine obviously," he said.

Relatives of the missing miners were told the machine had not been waterproofed and malfunctioned when water fell onto it.

Tasman Area Police Commander Superintendent Gary Knowles told a media conference this morning the earlier robot was sent into the mine at 6am and he was informed at 8am it had broken down.

Mr Knowles said rescuers were trying to get more advanced robots from Western Australia and America to deploy underground.

He said authorities were "pulling all strings" and the Royal New Zealand Air Force would fly in the Australian robot on a Hercules aircraft.

Experts today told the Science Media Centre that this morning's robot attempt was always likely to fail because the machine was not designed for the conditions.

'Kick in the guts'

Grey District Mayor Tony Kokshoorn said the breakdown of the robot had angered family members and made them question the rescue efforts at Pike River.

Hearing the high-tech Defence Force robot had short circuited after water from the ceiling dripped on it was a "kick in the guts" for them, he said.

"I'm only a lay person, my first thoughts were why didn't it have a bit of gladwrap over it, Mr Kokshoorn said.

"We were hanging our hopes on the robot because it can get around anywhere in the mine and tell you where our miners are and how they are. Without rescuers it was the next best thing.

"We walked in there and it was a kick in the guts. It's history. Imagine how that went down."

"People really started to be questioning of the procedures. There's a certain amount of anger coming up now. It was very emotional for everyone including myself."

Frustration turned to anger when family members after they were told a replacement robot was being flown in from the United States, he said.

"They asked why didn't they have a backup on their way already. Hell, it's desperate. It's so frustrating."

The trapped miners:
Conrad Adams, 43 (Greymouth), Malcolm Campbell, 25 (Greymouth - Scottish), Glen Cruse, 35 (Cobden), Allan Dixon, 59 (Runanga), Zen Drew, 21 (Greymouth), Christopher Duggan, 31 (Greymouth), Joseph Dunbar, 17 (Greymouth), John Hale, 45 (Ruatapu), Daniel Herk, 36 (Runanga), David Hoggart, 33 (Foxton), Richard Holling, 41 (Blackball), Andrew Hurren, 32 (Greymouth), Jacobus 'Koos' Jonker, 47 (Coben - South African), William Joynson, 49 (Dunollie - Australian), Riki Keane, 28 (Greymouth), Terry Kitchin, 41 (Runanga), Samuel Mackie, 26 (Greymouth), Francis Marden, 42 (Runanga), Michael Monk, 23 (Greymouth), Stuart Mudge, 31 (Runanga), Kane Nieper, 33 (Greymouth), Peter O'Neill, 55 (Runanga), Milton Osborne, 54 (Ngahere), Brendon Palmer, 27 (Cobden), Benjamin Rockhouse, 21 (Greymouth), Peter Rodger, 40 (Greymouth - British), Blair Sims, 28 (Greymouth), Joshua Ufer 25 (Australia), Keith Valli, 62 (Winton).