A volcanic alert was issued tonight on White Island, near the Bay of Plenty, following an increase in minor tremor levels.
GNS Science said minor activity this week had raised the alert to level one and the aviation code to yellow - indicating volcanic unrest.
The volcanic alert levels are from zero to five.
Volcanologist Brad Scott said jets of gas were being shot through the small lake and debris was ejecting from the volcano 20 to 30 metres into te air.
GNS Science said the activity was similar to that experienced in last July and then ash emissions the following month.