People in areas affected by the Mt Tongariro eruption overnight say they are concerned for their safety with the possibility of more volcanic activity.
The mountain rumbled into life just before 12am last night after 100 years of being dormant, spouting "flame-like explosions" and red hot rocks into the air, according to witness reports.
While Civil Defence cancelled the alert issued after the eruption because of subsided volcanic activity, GNS Science said there was a possibility it could blow again.
Some locals are nervous about being within a close vicinity of the mountain, taking precautionary measures in case of another eruption.
"Anything can happen from now on in so we're all on tenterhooks right now.
"We've just been into town to stock up."
Lake Rotoaira resident, Wayne McMahon, admitted he was "a bit anxious".
"I don't really want to go back (near the mountain), but I need to."
The eruption left a 6096 meter ash cloud hovering over the mountain, leaving around five centimetres of ash on State Highway 46 and noticed as far reaching as Napier.
McMahon, along with other locals, is also worried about what effect the ash could have on their livestock.
"This is our spawning time for the trout, so I'm not too sure how that will affect them now."
"We're really worried about all our animals over there. There's sheep, chickens, horses, cows," said Joy Campbell.
GNS Science said it was not ruling out further eruptions and expected heightened activity to continue for several weeks, but said it was too early to predict the next series of events.
GNS volcano surveillance co-ordinator Brad Scott said he would "really like to be able to tell us what's going to happen next," but all indicators point to the volcanic activity calming down.
However, Scott said there was no escalation of volcanic activity before the eruption to signal it was going to happen.
"There was no warning whatsoever. It just snuck up on us," he said at a press conference today.
Duty volcanologist Michael Rosenberg told TV ONE's Breakfast if past trends were anything to go by, it could be the first of many eruptions to follow.
"This might just be a quiet period and we should expect it to start again at any time. So we are watching things very closely," he said.
"This eruption caught us by surprise. We've been monitoring the area after earthquakes, but we didn't expect this."
Police said there was no immediate risk to the community, but they urged people to check their water supplies to make sure they had not been contaminated.
The Volcanic Alert Level for Tongariro was elevated from 1 to 2 and the Aviation Colour Code from yellow to red overnight.
The thick ash cloud stretching across much of the central North Island after the eruption caused flight disruptions, however flights to and from Napier are now the only affected.
Captain David Morgan, Air New Zealand General Manager Airline Operations and Safety and chief pilot, said the airline was working with the relevant authorities to safely make adjustments to flight routes to ensure aircraft remain clear of any ash and keep providing a safe service to the travelling public.
"We will not fly through ash and are constantly taking guidance from the CAA (Civil Aviation Authority) and the MetService to ensure we can continue to carry passengers where safe routes and altitudes are available," Morgan said.
Tongariro last erupted in 1897, although Ngauruhoe - geologically considered a vent of Tongariro - blew in 1974-75.
The GNS website also carries bulletins of volcanic activity on White Island, off the coast of Whakatane.