Preparations are being made to seal part of the Pike River coal mine in a first step toward retrieving the remains of 29 men who died in explosions there in November 2010.
A sealant called Rocksil will be pumped from the surface into a passage 2.3km into the mine later this month.
It will expand to 30 times its original size, sealing the mine.
Statutory mine manager Steve Ellis says air will then be re-introduced into the passage in preparation for drilling to reach the men's remains.
He says the sealant pumping is expected to begin on 16 January.