There was no confirmation last night that an exploratory bore hole had broken through, but a robot had been readied in the hope of entering the mine, possibly today.
Lawrie Drew, the father of Zen Drew, last night said he did not know how much longer people were going to be able to hold up without any news of their missing family members.
"People are getting really upset. I think people are really going to start losing the plot tomorrow if something doesn't change."
He said he got through each day trying not to think about it, lest it undid "all the good work I've done on myself to get me this far".
"I try not to think and then all of a sudden something reminds [me] of my boy, and I'm lost."
In other developments, a miner who survived the Strongman mining explosion disaster, just 30km from the Pike River mine, near Greymouth in 1967, suggested rescuers should have gone into the Pike River mine more or less straight away.
Ray Frew was working in the Strongman mine when an explosion occurred.
Of the 240 workers inside the mine at the time, 19 were killed.
Rescuers wearing breathing apparatus went into the mine within 20 minutes and the first bodies were brought to the surface about three hours after the explosion.
Grey district Mayor Tony Kokshoorn, who had said yesterday was crunch day for families desperate for any information of their loved ones, last night agreed tempers were beginning to fray.
"When you get into your fourth day of waiting, it's become really stressful, gut-wrenching."
However, most were holding it together somehow, he said.
"Until someone tells us there is no hope, we've got heaps of it."
As families struggled to deal with the lack of news of their family members, police last night conceded for the first time that lives could have been lost in the coal mine, from the 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.
It was still too dangerous for a rescue team to enter the mine, because of the possibility of heating underground, and gas analysis teams were taking regular samples to determine if there was active fire or heating underground that might ignite, Supt Knowles, the Tasman area police commander, said.
"We need to establish beyond reasonable doubt that an emission source does not exist.
"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."
An army bomb disposal robot was being readied to send into the mine, with a camera on board and dragging 2.5km of fibreoptic cable behind it.
It could go in before rescuers, but would not be sent in until they were sure sparks would not set off another explosion.
The robot would be capable of recording images but would also be equipped with simple things such as a rag tied to its arm to show movement in airflow in the mine.
"If it does that successfully [goes up the mine], then possibly it can go back up with other gas-testing devices or other equipment on board."
Pine River Coal chief executive Peter Whittall said a 15cm bore being drilled into the mine was 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 the risk of causing an ignition when it breaks through."
Once the hole was open, they could send down cameras and listening devices, as well as sample the air in that part of the mine.
Another group of family members travelled to the mine yesterday and, in contrast to reports to the contrary, Mr Whittall said the overwhelming feedback from them was not aggressive, and that they knew everything possible was being done to get their loved ones out.
- Additional reporting NZPA
