Mt Ruapehu has shown its power after an episode of volcanic earthquakes in the past week.
GNS Science says it "continues to closely monitor" the increase in seismic activity.
- Little-known eruption near NZ the biggest in 100 years
- Watch Auckland get wiped out by undersea volcanic eruption
"An episode of volcanic earthquakes is occurring beneath Mt Ruapehu," duty volcanologist Yannik Behr says.
"Since 15 March (NZ local time), GNS Science volcanologists have detected an ongoing sequence of seismic events beneath Mt Ruapehu that can be categorised as volcanic earthquakes.
"They have relatively small magnitudes and cannot be located by GeoNet's automatic earthquake detection system but the pattern of seismic recordings indicates a source beneath the summit area."
The crater lake (Te Wai ā-moe) temperature is currently at 39degC - well above the long-term distribution of measured temperatures.
"It is not unusual to observe volcanic earthquakes during phases of increased heat input into the lake," Mr Behr says.
"GNS Science continues to closely monitor Mt Ruapehu and our other active volcanoes through the GeoNet project."
Previous episodes didn't result in volcanic unrest, so the Volcanic Alert Level remains at 1.