Volcanologists are closely monitoring Mt Ruapehu after recording a volcanic earthquake swarm beneath the Crater Lake.
They have also noticed an increase in the lake temperature.
"We are uncertain of the implications of the recent observations," GNS duty volcanologist Agnes Mazot said.
"However, at this time these changes at Ruapehu are not considered sufficient to change the volcanic alert level.
"Swarms of volcanic earthquakes like these are uncommon on Ruapehu - seismic activity is usually dominated by volcanic tremor," Ms Mazot said.