Scientists say Mt Ruapehu's growing rumbles will not necessarily lead to a significant eruption.
Mount Ruapehu crater lake. Photo: AFP
The temperature is rising in the volcano's crater lake, the mountain continues to shake and it is discharging more and more sulphurous gases.
The volcanic alert level was yesterday moved from level one to two - moderate-to-heightened unrest.
But GNS vulcanologist Brad Scott said that was part and parcel of the life of a volcano.
"We perceive there may be some small-scale steam and gas driven activity contained to the crater lake. We're not looking at the likelihood of a significant eruption at this time."
Mr Scott said the Tongariro National Park was still a pretty safe place to go, although they were encouraging people not to go up to the crater.