Scientists are now confident White Island's latest eruptive episode has come to a close.

Following a small ash eruption on Tuesday, GNS Science volcanologists have been keeping a watchful eye on the offshore Bay of Plenty volcano.

"Observations made yesterday suggested that the eruption had ceased, and authorities had now lowered its Volcanic Alert Level to 2 and the Aviation Colour code to yellow. Analysis of ash collected on Wednesday shows no evidence that Tuesday's eruption was driven by new magma," GNS duty volcanologist Steve Sherburn said.

Instead, gas flow dragged recently loosened material to the surface, he said.

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"Seismic and acoustic activity remains low, and the gas flux from the island has not changed substantially since before Tuesday's eruption.

"Although Tuesday's eruption has ceased, White Island is always capable of a new eruption at any time, without prior warning."