An aerial observation was being conducted over Mt Ruapehu yesterday after temperatures in the active volcano's bubbling Crater Lake rose to the hottest on record.
On Saturday, a tourist flight over the Crater Lake observed "vigorous steaming" at the lake and disturbance of the surface itself with "upwelling bubbles".
This sort of activity had not been seen in years while Crown research institute GNS Science said a temperature of 44C was "the hottest lake temperature we have recorded since the new lake was established post-2000".
A flurry of volcanic earthquakes reported on Tuesday had now stopped. However, the seismic network at Ruapehu continues to record volcanic tremors.
GNS volcanologist Brad Scott had been closely monitoring activity overnight on Saturday and said there had been only more tremor and an insignificant change in lake temperature of around 0.3 of a degree.