Volcanologist warns of increased risk for sightseers to White Island after small eruption.
White Island has remained quiet overnight following yesterday's eruption, GeoNet says.
Duty volcanologist Nico Fournier said the activity remained at a low level, similar to that following yesterday's eruption.
There was still potential for further eruptions that may occur without warning, he said.
Civil Defence is continuing to monitor White Island as the eruption could be part of a sequence leading to a bigger event.
Following yesterday morning's blast, sightseers were warned another eruption could occur "at any time with little or no warning".
The alert status remained at level 2, and the Aviation Colour Code had been lowered from red to orange, Bay of Plenty Civil Defence said.
Yesterday's small eruption occurred at 10.23am, lasted for about 10 minutes and produced mostly steam. It was visible from the Bay of Plenty coast, with a plume rising to about 4km above sea level before slowly dispersing, said Emergency Management Group spokesman Clinton Naude.
Activity had since returned to normal.
"The eruption originated in the active crater area that has been experiencing very small mud eruptions in recent weeks," he said.
"The eruption threw mud and rocks a short distance from the source, and produced large volumes of white steam."
Weather radar observations showed a small proportion of volcanic ash was carried with the steam, Mr Naude said.
White Island has been experiencing low-level activity since last August.
Volcanologists observed a short period of strong volcanic tremors on Monday, however it was unclear if it was related to yesterday's eruption.
Hazards from the eruption were restricted to people on the island or possibly anchored nearby in boats, Mr Naude said.
The eruption did not affect flights.
Civil Aviation Authority spokesman Matthew Shore said the steam posed no risk to aviation.
GNS Science volcanologist Craig Miller said the eruption could be part of a sequence leading to a bigger volcanic event.
White Island has experienced several minor eruptions over the past year and volcanologists have found magma "very near" to the surface of the volcano, he said.
"We're not expecting it to stop in the next day or two."
There was no evidence to link White Island's volcanic activity to the Seddon earthquakes, Mr Miller said.
GNS had alerted tourist operators to the increased risk of heading out to the volcano, as eruptions on the island could happen at short notice, leaving tourists with no time to evacuate.
"It could be the one day that it goes suddenly wrong and you have very little time to prepare for it or do anything about it once you're out there."
The eruption would not trigger volcanic events at nearby areas such as Mt Tarawera, Mr Miller said.
* November 2012, Mt Tongariro: Thick grey smoke, gas and ash spews 4km into the sky from Te Maari vent on the western side of the mountain during an unexpected eruption.
* August 2012, Mt Tongariro: A volcanic plume shoots ash 7km into the air, forcing the cancellation of flights and postal services in Hawkes Bay.
* August 2012, White Island: Orange flashes light up Bay of Plenty skies and ash from the volcano drifts as far as Tauranga's coastline coating homes and cars along Papamoa Beach.