The aviation colour code at White Island has been raised from green to yellow after a strong tremor at the island.

GNS scientists recorded the tremor on Monday night, which was followed by a period of strong seismic activity, including a minor steam and mud eruption yesterday.

Duty volcanologist Tony Hurst says the minor eruption generated a steam plume, possibly visible from the mainland.

'Because these small eruptions have become more frequent the aviation colour code has been raised from green to yellow, but the volcanic alert level remains at one.”

Video from the web camera on the North Rim shows activity at 3.05pm to 3.20pm with jets of steam and some small slugs of mud pulsing above the inner crater rim.

Tony says volcanic tremor levels have increased since September 24, but are at lower levels than those during eruptive activity during the January and April period this year.

'Eruptions similar to those experienced over last 15 months are possible with no prior warning and have been occurring more often in the last week or two.”