Whakaari White Island's aviation code has been raised, due to small amounts of volcanic ash from the Bay of Plenty Island

GNS Science has issued a volcanic alert, upgrading the aviation colour code to orange.

The volcanic alert level remains at two, which indicates moderate to heightened unrest.

Duty Volcanologist Craig Millar says the volcano's been emitting weak to moderate steam and gas plume over the past two-to-three weeks.

He says they're continuing to monitor the island through remote cameras and satellite imagery.