Small earthquakes have been detected under Mount Tongariro over the past two weeks but GNS Science says they are too small to cause major concern.
However, duty volcanologist Michael Rosenberg says the quakes are interesting because there has been so little activity at Tongariro since it last erupted in November 2012.
He says before that eruption, there was a similar swarm of earthquakes in roughly the same area.
Mr Rosenberg says he doesn't believe there's any risk of an eruption at this stage because the quakes are tiny and gas levels in Mt Tongariro remain unchanged.
GNS Science is, however, warning that an eruption could still occur with little or not warning. The volcanic alert level remains at level one, which indicates volcanic unrest.