Solid Energy says work on part of the re-entry plan into the Pike River mine should be completed by Christmas.
Twenty-nine men died after a series of explosions at the West Coast mine that began on 19 November 2010.
Last month, the Defence Force finished the first stage of the project by removing 35 tonnes of debris from the ventilation shaft.
Solid Energy says contractors have started to plug the shaft by placing a high strength expanding resin into it.
Solid Energy crew on the Pike River mine vent shaft platform. Photo: SOLID ENERGY
Project director Mark Pizey says once the resin is set, the shaft will be filled with another material which will be topped off with a layer of concrete.
Mr Pizey says the shaft needs to be sealed to stabilise the environment in the mine.
The bottom 40-50 metres of the shaft - originally about 100 metres deep - is filled with rock from an earlier collapse.
Planning is also underway for the project's next phase - drilling additional boreholes into the main tunnel.
The first helicopter-lifted load of concrete is sent in. Photo: SOLID ENERGY
