The first of a series of explosions over several days struck the West Coast underground mine on November 19 with 29 men unaccounted for since.

Work to inert the mine has also faced many challenges including the isolated and difficult terrain, high methane levels underground, and difficulties controlling the amount of oxygen getting into the mine.

Police Commissioner Howard Broad detailed the reasons for his decision.

Broad’s statement yesterday

I've been in Greymouth this afternoon to personally update the families of the Pike River workers and contractors on the Police's recovery operation.

I came here before Christmas and then I said that access to the mine to recover the remains of the men was desirable but not legally essential, given advice I had received by the Coroner.

I reiterated, though, that we would do our level best to achieve recovery of the men, but not through the means of putting additional lives at risk in terms of anyone else re-entering the mine.

I also indicated at that time that the responsibility for the mine ought to go back to the Pike River Mine company whose mine it is, but the company almost immediately went into receivership and that made the circumstances even more difficult.

We have remained with the operation since then. Our aim has been to recover the men and to do that by bringing the mine into a stable state.

We requested from the Pike River Mine management a plan by which our objective could be accomplished. The company has provided us with a proposal, but it raised many questions.

After assessment of that proposal by a panel of experts, I went back to the company to ask them those questions that were raised. I since have had a reply to that presentation of questions and, frankly, my confidence in terms of a recovery operation to bring the men out is, as a consequence, quite low.

While it is possible to argue a technical case that access to the mine is possible, it is, in my view, impractical to expend much hope on that prospect.

In forming a view on this I have had advice from experts from Australia and New Zealand and from Australian and New Zealand mines rescue personnel.

The assessment is that the likelihood of getting into the mine is unrealistic because it is too unsafe.

I also had an experienced mine manager from Australia do an objective assessment of the arrangements that had been put in place, the questions and answers that have been given and received a similar reply.

Based on all this advice it would have been quite wrong for the Police to hold out great hope that the men will be recovered and I have decided that the recovery phase of this operation will come to a conclusion.

The means of concluding this operation is by handing the mine back to the receiver who controls Pike River Coal mine. I have written to the receiver today, outlining this point, and inviting him to immediately reply to this step.

A key responsibility for the receivers will be securing the mine safely while it determines its next steps in its course of action. Both the Police and the Department of Conservation have an interest in seeing the mine is properly secured in a stable state and we will be having further discussions with the Receivers on these matters.

In my view it is now time to focus on the living and to respect and memorialise those men who have died.

I have thanked the families for the way in which they have dealt with this most heart-rending of tragedies and I am gratified by the response that has been received by the Police from the families.

I want to also thank my team here led by Superintendent Gary Knowles for the job they have done during these last few months.

To put together an incident response arrangement of such magnitude and under such circumstances is a hugely challenging task and I believe it has been accomplished extremely professionally by those from the Police and those we have asked to support this operation.

We are disappointed that we are not in a different state to [that] we are [in] today.