The White Island volcano off the Bay of Plenty coast erupted this morning sending a plume of steam into the air visible from the mainland.

GeoNet confirmed the volcano erupted for 10 minutes at 10.23am sending mostly steam into the air that reached about 4km above sea level.

Activity has now diminished to levels before the eruption and the aviation alert code has been reduced from red to orange – meaning heightened unrest.

White Island erupting about 10.25am. Photo: Alex and Jennifer Simon.

GeoNet Duty Volcanologist Nico Fournier says the eruption originated in the active crater area that has been experiencing very small mud eruptions in recent weeks.

'The eruption threw mud and rocks a short distance from the source, and produced large volumes of white steam. Weather radar observations show that a small proportion of volcanic ash was carried with the steam.

White Island has been experiencing low level activity since August 2012 so an eruption like that this morning was not completely unexpected, says Nico.

'Volcanologists observed a short period of strong volcanic tremor yesterday morning, but it is not clear if this was related to this morning's eruption.”

Duty Volcanologist Nico Fournier says it is too soon for any kind of prediction of activity in the next few days.

'Given the low level of activity over the last year we are watching carefully and would not be surprised if there were further eruptions in the next few days”.

GNS volcano geophysicist Steve Sherburn earlier told SunLive scientists could not say whether the eruption is linked to the recent Seddon earthquake swarm.

'The short answer is we don't really know - it's difficult to tell. We had a strong period of tremor about 24 hours ago and someone asked the same question. The answer is, we don't really know.”

The volcanic alert level is at 2 meaning minor eruptive activity while the aviation colour code lowered from Red meaning an eruption is imminent to orange meaning heightened unrest.

Nico says this morning's eruption only posed a risk to anyone on White Island or anchored nearby in a boat.

'Anyone living in the Bay of Plenty is not at risk.”

White Island Tours had a boat full of tourists out visiting the island this morning who witnessed the eruption.

Marketing manager Patrick O'Sullivan says the boat was a fair way off the island when they noticed more steam than normal.

'They went out to the east where you can see in to the crater and at that point they did see the eruption occur.

'They saw a whole lot of steam and there may have been some ash in it, but they were a fair way off.”

Patrick says the company keeps in contact with the other two helicopter tourism businesses operating on White Island and believes there was no one on the island at the time of the eruption.

'Until GeoNet gets scientists out there we won't be going on the island, hopefully we'll be back to normal tomorrow."

White Island Tours has been operating for 23 years and Patrick says there have been times in the past when the island has been more active than what was witnessed earlier today.

A Pukehina Beach resident watched the eruption from his coastal home today and says the steam reached 3000-4000 metres in the air.

'It's just started recently, I just noticed it – it's a big, big cloud several thousand metres high.”

The resident, who did not want to be named, has lived in Pukehina for 16 years and says this is the first time he has seen anything like it.

White Island is the country's most active volcano.

White Island erupted this morning sending a steam plume into the air visible from the mainland. Photo: Lani Hepi.