Work is continuing to stabilise the Pike River Mine but any recovery of the 29 miners killed in explosions there last year is still some months away.
Mine manager Steve Ellis says a temporary air lock has been installed about 170 metres into the mine.
But he says another seal at the mine's entry which was created just after the incident is not fit for the purpose and is now being replaced.
Mr Ellis says options for re-entering the mine include a staged entry or boring down and creating another remote seal further along the mine passage.
He says the miners' families have been kept informed of the time frames.