Police have officially named the 29 miners trapped in the Pike River coal mine on the West Coast since Friday.

At a 10am media conference, Tasman District police area commander Superintendent Gary Knowles read out the names and ages of those missing.

"It is really important that we start putting names to our people, so that people know who they are and they are not nameless faces," he said prior to reading them out.

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).

The names of the miners have also been posted on the police website.

Mr Knowles said after three days without contact the situation remained "grave" but he said drilling at the site was continuing and progress was going well.

He said the Department of Conservation, which owns the land where the mine is sited, had agreed to allow a 2.7km path up to the main ventilation site to be cut, making it easier to take air samples.

The site is currently only accessible by helicopter.

Mr Knowles said rescuers were also looking at getting a fibre optic cable so that the site could be monitored visually from base camp.

Mr Knowles said the rescue team remained on standby and were looking at what sections of the mine they could enter first.

"We've also been in close contact with the defence department and will be utilising if possible a robot on site to go into the tunnel when the opportunity arises.

Mr Knowles said they plan to also use seismic equipment on top of the ground to detect movement underground.

Testing of the gas levels in the mine was being carried out every half hour and so far remained unsafe.

"We remain optimistic," Mr Knowles said. "But at the end of the day this is a search and recovery operation. We are going to go in and do our best to bring these guys to out."

Pike River CEO Peter Whittall said the team drilling overnight had done a "phenomenal job" and had reached 100 metres of the 162 metres they needed to drill to.

"In the last 10 metres before we get to the scene we will change drilling method to ensure we don't get any sparking," he said.

"We have opportunities to sample gas from that point. We will have an opportunity to put laser imaging gear down the hole.

"We will also be able to put down video camera information and look at anything we are able to see in the hole."

He said the Defence Force robot would not be sent into the mine while there was any chance of it causing a spark.

Mr Whittall said the blast was "a unique event".

"At the time of the incident there was an unsafe incident. Otherwise this would not have occurred."

Mr Whittall said buses would be available to take families back to the site later today.

He asked media not to speculate.

"There's a lot of speculation. The only ones that really know what is going on is the people who are on site."

Prime Minister John Key also addressed media, saying these were "very testing and difficult days for Greymouth, which is a tight-knit community".

"There is no question that the families are showing high levels of fear, anxiety and frustration. But we owe it to the men that are underground that we undertake a rescue that does not endanger their lives any further," Mr Key said.

"We are going to get through this and do everything we possibly can to get the men out alive. That is our single focus at the moment," he said.

"In due course there will be a time to reflect what went wrong and what lessons can be learnt. It goes without saying there will be a number of inquiries."

Asked whether he would consider closing down the mine permanently, Mr Key would not be drawn.

"You are asking us to speculate on something we don't know. Let's what and see what pans out. But whatever happens here there will be an inquiry or several inquiries and we will need to ask ourselves some tough questions," he said.

"When these mines were started it was done so on the knowledge it was safe. We would not have allowed anyone to go into the mine if it wasn't."

He said the cause of the explosion was unclear and he didn't want to jump to conclusions on the stability of mines in the area.

Mr Key said he had received messages of support from international leaders including United States President Barack Obama.