A section of the Mauao base track has fallen away in a large slip.
The slip exposes a drop of about 30m above where the track used to be and was on the Pilot Bay side of the mountain approaching the beach.
Parks and Recreation manager Mark Smith said he did know how long it would take to repair the slip or to restore public access to that part of the track.
''Previous slips of this type on Mauao have taken weeks, and sometimes months, to restore safe public access. Unfortunately, the base track will not be open as a complete circuit for some time.''