The chief inspector of mines is optimistic a plan to re-enter the Pike River Coal Mine could be completed in the next few months.
Bernie Monk, a spokesperson for some of the families of the 29 men who died in explosions in the mine in 2010, has said he is hopeful a plan to re-enter the mine will be in place by the end of August. Tony Forster, the chief inspector of mines, says that timing may be about right.
Mr Forster says his High Hazards Unit will have to assess whether the plan is safe, viable and economical.
He says he has been working closely with the risk assessment group putting together the plan, and he believes the plan will meet requirements.
Police told families of workers in Greymouth on Wednesday night there was insufficient evidence to lay manslaughter charges, even though there was ample evidence of widespread departures from accepted standards of mine operations.
They said there was enough evidence to lay a charge of criminal nuisance but if police did pursue that prosecution it could interfere with ongoing prosecutions brought by the Ministry of Business, Innovation and Employment under the Health and Safety in Employment Act.
Detective Superintendent Read, who led the inquiry team, said if the mine was entered in future new evidence could prompt police to revisit the case. However, he said there was no guarantee that new evidence would lead to a prosecution.
Mr Monk says the families were heartbroken at hearing the police decision but will take steps to gain more evidence.
"In August of this year we'll be putting the plan of getting into the mine and we'll be able to answer a lot of these questions for the police. We'll be able to sit back and say to the police 'we told you so' and we'll be quite happy then."
Mr Monk says they are discussing legal options they might pursue to hold somebody accountable for the deaths. "Things like departments could be looked at here, and individuals, so we've got options to take."
Neville Rockhouse, whose son Ben died, says the news reinforces the need to re-enter the mine. "As the police said, a scene investigation could change things. I want to get the guys out. In doing that I think it meets the dual purpose of providing police with the scene examination that they need."
Detective Superintendent Read told Radio New Zealand's Morning Report programme on Thursday investigators consulted a wide range of experts, but in the end, did not have sufficient evidence to press manslaughter charges.
"We had to establish that there was an individual responsible for an act or an omission that led to the explosion and we couldn't get that causal link. We couldn't actually say that this act caused the explosion when we had so many options available for the explosion."
Lawyer Colin Smith who represents some of the families says they will continue to pursue a civil lawsuit and will look at involvement of individuals, the company and regulators including the former Department of Labour.
The MP for the West Coast, Labour's Damien O'Connor, says police should have also investigated the former Department of Labour, which he said had provided advice saying the mine was safe as recently as a month before to the Minister.
"In my view that advice was completely flawed and does beg the question whether any liability should apportion to them."
Mr O'Connor said the decision not to prosecute Pike river Coal also demonstrates the need to introduce corporate manslaughter laws.