Magma bubbles higher in Mt Tongariro
Tests have revealed that magma is bubbling higher than usual in Mount Tongariro, which means further eruptions are more likely.
A series of samples have been tested since the volcano's Te Mari crater erupted on Monday night, but the latest results give the greatest insight.
"We're now convinced that the likelihood of this just being a one-off has decreased," GNS vulcanologist Nico Fournier said.
"But it doesn't mean it's just about to blow and go pear-shape."
The results detected sulphur dioxide and carbon dioxide in the steam plume, which indicated that magma was closer to the surface than it usually was, Fournier said.
It was unclear how high the magma was - it could be anything from metres to kilometres, Fournier said.
If a magmatic eruption did occur then it wouldn't necessarily be significant, he said. It could result in a lava flow or it could lead to a series of explosions.
"It doesn't mean it could be a massive eruption, it could be passive," Fournier said.
It was also likely that Monday night's eruption could be followed by a series of steam eruptions, or no activity at all, Fournier said.
Civil Defence, along with a number of other organisations including the Department of Conservation, would continue to monitor the volcano's activity.
There was no new advice or warnings that stemmed from the latest development, a Civil Defence spokesman said.
There was about 2100 tonnes of sulphur dioxide being emitted from the volcano per day.
That was above average and the highest suplhur dioxide emission rate for any New Zealand volcano, however it wasn't unexpected considering the amount of steam and gas which was being emitted, a GNS spokesperson said.
Further visual observations were being undertaken today.
Scientists would also be obtaining gas and water samples from the nearby Ketetahi hot springs and some of the rocks which were ejected from the crater and which damaged the Ketetahi hut.
The volcano was still ejecting steam and gas this morning while tremors continued to shake the earth below it, Fournier said.
Meanwhile, a 4.7 magnitude earthquake in the Bay of Plenty this morning has had no impact on White Island, which erupted on Tuesday night.
It was the first eruption in 12 years for the country's most active and largest cone.
White Island tended to have volcanic episodes which lasted a few months to a few years, so this could just be the start of more to come, Rosenberg said.
The Te Mari crater last erupted in 1897.