Gas levels in the Pike Coal mine where 29 miners are trapped are "coming down", but are still fluctuating.
Police Superintendent Gary Knowles said any rescue bid was still some distance away, saying there would be no "quick-fix" to the rescue operation.
However he reiterated the focus was still on rescuing the 29 trapped men.
He said the rescue effort was "still dependent on the reduction on the level of gases in the chambers [the mine]."
* A rig will drill a 150m hole to test air quality in the mine
* A full inquiry will be held after the emergency is resolved.
* Two busloads of family members travel to the mine to speak with rescuers
* Gas levels in mine continue to trend down
They are our brothers - rescue chief
Mines Rescue NZ general manager Trevor Watts revealed a Mines Rescue member was one of the men trapped underground, and said if there was the "slightest opportunity" to move in, the team would take it.
But he said conditions in the mine were still too dangerous to send men in.
Watts said that "the whole of [the trapped miners] are our brothers".
"The whole lot of them are our brothers and we know all of these guys there and if there was the slightest opportunity to go underground then we will be going."
He would not send rescuers to the area where miner Daniel Rockhouse and mine electrician Russell Smith escaped from.
"It's still in the gun barrel. They are still in part of the mine. They are still in direct travel of an explosion path"
Pike River CEO Peter Whittall clarified comments about what the temperature would be for the trapped miners.
He said an earlier statement that they would be in 25 degree heat was based on an assumption they were sitting in a fresh air source.
That would be different if they were near the site of a heat source or suspected fire still burning in the mine.
Support for families
Buses this morning took representatives from the families of the missing miners to the site for a short visit. The group returned at 12pm.
In a press conference this afternoon Mr Whittall said he'd spent much of the day with families, taking them up to the mine to speak with rescuers and emergency staff.
Mr Whittall said the trip was "successful", and that families were "very appreciative".
He said discussion with the two miners who'd escaped the blast had provided little additional information, with the two men not deep enough in the mine to offer any insight into the fate of the trapped miners.
Earlier, Grey District Mayor Tony Kokshoorn, who is in regular contact with the families, said this morning there was a period yesterday of "bottom-line despair" when rescue workers had to be taken off the mine site. Hopes had lifted slightly today because those teams were back at the site.
"There's no doubt about it, there is a lot of despair amongst them," he said.
"There's a sober feeling amongst them all. They are just trying to buoy themselves along and encourage each other as a community, and holding on to the vision that the search and rescue exercise will activate at any time."
Mr Kokshoorn said the families continued to hope that they could hear news of a "fantastic outcome" as the families of the 33 miners recently trapped in Chile had received.
"At the same time, these people have lived on the West Coast all their lives and they are realists. They know the degree of danger in here. They know the degree of where it could go from a negative point of view. But there's no point being that way."
Until someone told them that the men could not be brought home, the families would continue to hold on to their hopes, Mr Kokshoorn said.
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