Rocks and mud are being thrown from the White Island crater as tremors within the volcano continue.

GNS Science vulcanologist Brad Scott said a visit to New Zealand's most active volcano this morning registered slightly less-frequent tremors, but the tremors were still relatively strong.

"Early this morning the continuous volcanic tremor which has been recorded during the [past] few weeks at White Island has changed to a pattern of intermittent tremor," Scott said.

"When occurring, the volcanic tremor remains strong.

"The current level of unrest means that there is a greater-than-usual hazard to visitors." The visit revealed the crater lake was drying out and the frequent bursts of mud, steam and gas were still being shot at least several tens of metres out from the lake area.

Steam and gas clouds above the volcano could be seen from the Bay of Plenty coastline.

Shifting magma within the White Island crater prompted an upgrade to the mountain's aviation alert code to orange last week.

White Island was still at an elevated level of unrest but Scott said the amount of gas being ejected from the crater did not necessarily suggest a large eruption was imminent.

"GNS Science's past monitoring of the island shows that weak ash eruptions have often followed drying out of this type of mud-filled lake," he said.

"More vigorous explosions of mud, rock and perhaps molten sulphur are possible in future with little or no warning."

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