Work to plug the ventilation shaft of the Pike River mine on the West Coast has been delayed by weather conditions and any entry into the mine won't happen before the end of April.
The mine exploded in November 2010, killing 29 men who were underground at the time.
Owner Solid Energy said on Thursday that the bulk of the ventilation shaft has been filled and expanding foam is being placed in it to fully seal it.
The company said the weather so far this summer has allowed fewer work days on the vent shaft platform, which can only be reached by helicopter.
