Over the coming weeks GNS will be looking at what caused White Island to be upgraded to volcanic alert level three after a mini eruption last week.

The alert level has now been dropped back to its normal level one following last Tuesday's incident.

Volcanologist Brad Scott said there are currently two or three really big steam vents under high pressure producing a lot of gas.

Mr Scott said the next step is to gather debris from the walls of the vents, while the alert level may also fluctuate up and down.

"Now that this has happened, there is obviously some instability in the wall of one of them at least - if not two of the vents."

"We may just end up popping backwards and forwards between nothing and something."

Scott said there has been no heightened volcanic unrest above what White Island normally produces.

"We don't have elevated seismic activity or acoustic activity or gas output."

"Therefore we have just dropped back to level one, which is just the normal level of volcanic unrest for White Island."

GNS said observations over the weekend indicate no further sustained ash, and seismic activity is low.

The aviation alert colour code is yellow.