Scientists and Bay of Plenty Civil Defence staff are keeping a watch on White Island off the region's coast this weekend as seismic activity increases.

GNS scientists noticed late this week the type of seismic activity at White Island had changed.

Scientists believe White Island could erupt at anytime without any warning.

While the level of volcanic tremor began to decrease, ‘hybrid volcanic earthquakes' had appeared.

Hybrid earthquakes are typically associated with movement of molten material (magma) within an active volcano.

GNS scientists took a gas flight over the volcano yesterday which showed a level of gas emitted was similar to last month.

A mud geyser is continuing in the Crater Lake and earthquake activity remains above background levels.

Civil Defence Emergency Management Group controller Warwick Murray says the current episode of activity started in August 2012 with explosions and ash emission and in November a small lava dome appeared.

'Volcanic unrest has been increasing since about January 14. Increased hydrothermal activity in the ‘hot lake' has been described as some of the most vigorous seen for many years.”

Warwick says future eruptions are possible with little or no warning, meaning an increased hazard to visitors to the island.

'Hazards can include the health effects of volcanic gas exposure, respiratory issues, skin and eye sensitivity to acid gases. Explosive eruptions can occur at any time with little or no warning. A high level of caution should be taken if you are visiting White Island.

'Scientists are not sure what could happen next. Magma could flow underground with no changes in surface activity and there could be more dome building as in November or explosive eruptions and ash emissions, as in August last year.”

He says there is little risk to the mainland from this seismic activity, but we understand that people are concerned.

'Visitors to White Island should ensure that they informed, and must exercise high level of caution. If you are boating near the island throughout the long weekend, monitor marine channels for updates and exercise caution.”

Meanwhile, the Volcanic Alert Level for White Island remains at 1, indicating signs of volcanic unrest.

The alert level ranges from 0 to 5.

Because of the change in activity and increased level of unrest, the Aviation Colour Code has been lifted from yellow to orange.

Aviation Colour Codes have four colours – green, yellow, orange, red as a quick reference for planes flying in the area.