Photo: Supplied / Murry Cave
Gisborne District Council is warning people to avoid a section of the Hangaroa River after a massive landslide.
It said people should not try to access the river below Bushy Knoll Road.
The council's principal scientist Murry Cave said the land is very unstable after a landslide in late June.
He said the landslide has a lot of unstable material which is holding up a large volume of water, and it could fall at any time.
"We expect this landslide to fail with little notice at any time. If it does fail there is a possibility that a debris flow will be generated which may reach the Hangaroa River and travel downstream as a debris flood."
Cave said it is likely to fall during or after heavy rain - but it could fail even without rain triggering it.
"Anyone considering accessing the Hangaroa River below Bushy Knoll Road should, for the time being, avoid the river until such time as council advises that the landslide has failed or has stabilised.
"We have observed a number of such failures in the last month."
Anyone who sees any unusual activity on their land should contact council.