GNS Science reported that the eruption, between 9.30pm and 11pm yesterday, appeared to have deposited material over the north side of the floor of the crater and up on to the north crater wall.
It came with moderately elevated seismic activity, but levels had returned back to normal.
There was not yet a clear view of the crater visible from CCTV cameras on the island and GNS volcanologists were monitoring the situation.
Meanwhile, the island's Volcanic Alert Level had been elevated from 1 to 3, meaning a minor volcanic eruption had happened.
The aviation colour code had changed from green to orange, meaning the volcano was exhibiting "heightened unrest with increased likelihood of eruption" or that an eruption was under way with no or minor ash emission.
Over the past couple of weeks, GNS scientists had observed a fall of 2m in the water level of the island's crater lake.
Despite this, they hadn't noted any changes in other monitored parameters like the amount of volcanic gas being emitted, fumarole temperatures and volcanic tremors or earthquakes.
On the last visit, GNS volcanologist Brad Scott confirmed the lake level had dropped 2m in the past fortnight and that its levels had returned to what they were in 2014.
The drop in water level of the lake had also revealed several islands or crater outlines and the lake temperature has increased from 56C to 58C since February.
There had been a small decrease in the temperature of the hottest fumarole -- from 169C to 161C -- since February, while outputs of sulphur dioxide had ranged between between 90 and 480 tonnes a day during the past five weeks, which were typical values for White Island.
In 2012, the 2km-wide, 321m-high, circular chunk of rock 48km off the Bay of Plenty sprang back into life over two months, ending more than a decade of peace.
A series of quakes soon escalated into something scientists hadn't witnessed in New Zealand for a half a century -- the volcano extruded lava, appearing on the surface as a black, craggy lava dome, plugging magma just below the surface.
This was followed by heating in the crater lake and steam explosions in early 2013 which removed the lake.
By June that year, the lake was back, although eruptions followed in August and October.
Unrest has continued, but scientists say eruptions shouldn't worry people.
An eruption would likely have little or no effect on the mainland 48km away -- nearly all previous eruptions had only affected the island itself -- but under certain wind conditions, a light ashfall could carry a fine layer of pollen-like ash.
