Scientists monitoring volcanic activity on Mount Tongariro say earthquakes have again increased under the mountain.
GNS Science started recording earthquake activity this month and while it started to decline last week, it has now picked up again.
GNS says between three and 10 quakes are occurring each day.
The volcanic alert remains at level one, on a scale of six.
GNS volcanologist Brad Scott says the earthquakes cluster is in a zone between the mountain and Lake Rotoaira, at a depth between 2km and 7km, and most are unlikely to be felt.
He say gas samples are being taken and a GPS instrument has been installed to detect ground movement.