International mining experts looking into the feasibility of re-opening the Pike River mine say it's still too early to say if it can be entered safely.
David Feickert, a former mine safety adviser to the Chinese government; David Creedy, an international methane gas expert and Bob Stevenson, a former chief inspector for all mines in Britain, are spending the week in Greymouth at the request of the families of the 29 dead men.
They began their research with a flyover of the mine and a site visit with representatives of the mine owner, Solid Energy, on Wednesday.
Mr Stevenson said access will be difficult but they now have an idea of where they would like to place new bore holes to help reventilate the mine.
But he said he is not yet prepared to say whether a re-entry will be achievable.