The Pike River Mine will be treated as a "crime scene" when the return finally takes place, the government says.
The responsible minister, Andrew Little, told Checkpoint that the re-entry planning is now at a very detailed stage.
"We are about to have seconded a senior policeman, a sergeant to a detective, two or three days a week to the group, because once it is introduced, it will be treated as a crime scene and there will be forensic work necessary. "
That forensic work could reveal more about the cause of the explosions that killed 29 men in the mine in November 2010.
If that happens, and if the evidence gathered is strong enough to support prosecution, Mr. Little said that an indictment of manslaughter or indictment was possible.
But Mr. Little said it is important not to exaggerate that possibility to families who have been exhausted by eight years of waiting and are not being fulfilled by promises.
"We do not rule out anything, I do not want the families to think that this is a breeze, we get in there, we get some evidence and then we can take prosecutions very carefully."