There is frustration among some families of Pike River, who are calling for better technology to be used in the recovery mission.
The operation at the mine is continuing to make progress, with workers now 1980 metres in.
Families spokesperson Bernie Monk is urging the Pike River Recovery Agency to use higher standard measuring equipment, which he says can provide more reliable results.
Next month marks a decade since the mining disaster which killed 29 men.
The recovery agency provided an update on the progress yesterday.
The agency's chief operating officer, Dinghy Pattinson, said despite losing two months to Covid-19, work is progressing well thanks to changes in the way they work.
"We used the opportunity in Covid to think, what can we do differently, how can we make up the eight weeks we lost?"
He said changes in roof bolt installation meant it now takes 15 minutes to install, compared to the previous time of 50 minutes.
Workers are also putting in more hours, with 90 hours of work being put in over a fortnight, compared to the previous 80 hours.
Pattinson said it has been done in consultation with staff along with risk assessments.
The agency's chief executive, Dave Gawn, said it is on track to finish and move out of the mine by the end of December.
It will then hand over the mine to the Department of Conservation in March.
He said there is considerable damage inside the mine.
"There is significant damage from four blasts, and, yes you expect it but you don't actually realise how significant it is until you actually get eyes on," Gawn said.
Pattinson said at this stage, no human remains have been found, but concedes it could be a possibility.
"The police are on site the whole time so they would know if anything is found and they have a process where it involves the coroner and notification of families and so forth," he said.
Better technology urged
The process is frustrating for some family members, according to long-time spokesperson Bernie Monk.
He lost his son, Michael, in the disaster.
Monk called on the agency to start using Lidar scanners - which use lasers to accurately map areas.
"In the old days you know how when they used to have car accidents and they used to do it by taking measurements in chalk?
"Well that's the sort of the situation where the poor guys that are doing it underground - and the miners are doing a fantastic job - but the way that they are having to do it is antiquated and it's frustrating."
The agency said there are no approved Lidar scanners available for use in underground coal mines in New Zealand although it has been looking at a recently certificated Australian Lidar scanner that could be used here.
But Monk said an overseas expert has told him that it can be used in New Zealand mines .
"Shouldn't have all this been worked out long before now? Why is it because we bring things up - the families - that they make it such a difficult issue to be able to get things done?" Monk said.
The Pike River Recovery Agency said the next step in November is to reach the foam plug, which separates the fresh air atmosphere in the drift, from the nitrogen and methane atmosphere of the mine workings.
Once passed the plug, workers will reach their final destination - the rockfall inside the mine.