Locals have criticised the response to last night's Tongariro eruption as too slow but authorities have defended their procedures, saying they quickly established there was no immediate risk and put plans in place.
The hydrothermal eruption occurred at 11.50pm, but it took almost two hours for a Civil Defence warning to be issued.
The local community put its own emergency plan into action, with community liaison personnel getting in touch with residents.
Some 24 locals in the area chose to evacuate to Hirangi Marae last night, with most returning to their homes this morning.
The action plan was developed after a meeting last Tuesday, involving staff from GNS Science, the Department of Conservation (DOC), police and Civil Defence, to discuss recent volcanic activity.
Lake Rotoaira resident David Bennett, who lives about 6km from the eruption, said the community did everything right but the official response was too slow, with no police seen in the area until about 7am today.
"They've been up and down the road, but they haven't called into any of the houses. They're talking about people going out and doing bits and pieces, but they've done nothing - we've done it all ourselves."
He said authorities had got their initial information "second-hand from our people".
"That's the problem - all these big organisations do all the talking, but they don't have anyone on the ground. At the end of the day, DOC look after the mountain, but they don't live here, if you know what I mean."
He said the area was "pretty isolated" so locals needed to respond themselves.
"We live here, and it's a long way to travel from Taupo or places to get here - it's at least 20 minutes from Turangi, an hour from Taupo."
Before last night, there had been "little bits of smoke" and the smell of sulfur - but no warning of what was to come.
"People were prepared, that's the main thing. We had a good infrastructure where people went and checked all their neighbours and made sure the older people were sorted, and no worries at all."
Tuwharetoa community coordinator Bubs Smith, who was the first point of call for officials, said the community was "a lot more informed" after last week's meeting, which was attended by up to 60 locals.
"We don't see it as a role for police to come and lead us hand-in-hand around, and for an initial response anyway, we're the best ones to actually get that initial response up and running."
Mr Smith was on a teleconference call with DOC, GNS Science, police and Civil Defence staff by 12.45am today, which gave authorities an idea of what was happening.
He said everything went to plan in terms of contact, and he thought police and Civil Defence had acted fast enough - especially given the time the eruption occurred.
"You could probably argue and say that yeah, this could have been done a little bit quicker, and hey there's some learnings that we may have to look at - how can we sharpen up things a little bit quicker?
"But for what happened, the response was quite adequate I think."
Taupo police area commander Inspector Steve Bullock said all the agencies with a vested interest in events like a volcano were communicating and liaising with local iwi "from the outset".
"The first priority in terms of public safety was closing the roads and assessing the risk to local residents.
"It was quickly established that the situation was very confined, there was no immediate risk to anyone outside of the park and no requirement for evacuation. Some residents chose to self-evacuate to the Hirangi Marae.
"Once we were satisfied that the residents were safe, attention was turned to the park itself, and police, search and rescue volunteers and DOC staff set about checking the tracks and the huts in the area.
"We are satisfied that our standard procedures were effective."
DOC Ruapehu area manager Dr Nic Peet (correct) said its priority was public safety and providing reassurance to those who were affected.
"The situation is very much a localised situation and we have the police and scientists working closely with us to ensure our response is at the appropriate level."
Bunk beds inside DOC's vacant Ketetahi Hut were destroyed by boulders, measuring one-metre across.
The explosion flung them 1.5km before they smashed into the hut, causing serious damage.
Mr Peet said the boulders had punched holes in the roof and floor of the hut.
"There was certainly significant damage to the hut so people could have been injured or killed if they'd been inside it."
After the search this morning, three men were walked out from Mangatepopo Hut which was unaffected. No-one was occupying the other two huts.
All four DOC huts around Mt Tongariro will remain closed for safety reasons.
The police-led search and rescue operation on the mountain has been completed, with no-one found to have been killed or injured as a result of the eruption.
Tracks on Mt Tongariro will also remain closed in the immediate future while GNS experts continue to assess volcanic activity on the mountain.
Civil Defence spokesman Tony Wallace said GNS Science was constantly monitoring the situation and gave its assessments to Civil Defence whenever there was unusual activity.
Civil Defence then determined its response.
"We certainly made a decision to put an advisory out fairly soon after we got all the information we needed," he said.
"It's a combination of technical information and then human assessment of that information."
Mr Wallace said information coming in from regional Civil Defence groups was also "vitally important" to the response.
He said it was "quite common" to have some warning of activity when an eruption was imminent - but that had not been the case this time.
Civil Defence was keeping a close watching brief, and would continue to advise on the situation.
GNS Science duty volcanologist Michael Rosenberg said the eruption had come as a surprise.
The volcanic alert at Tongariro was lifted on July 20 to level one - indicating "signs of volcano unrest" - after a series of small earthquakes below magnitude 2.5.
After last night's eruption, the alert level was lifted to two, indicating "minor eruptive activity" .
"We really didn't expect this sort of situation to happen, certainly in this time frame, and given that those small earthquakes were declining in the last week or so, we were considering perhaps the whole thing was quietening down," Mr Rosenberg said.
"It really has taken us all by surprise. The sort of changes in the types of earthquakes - moving to continuous volcanic tremors, that you might expect just immediately before an eruption - we didn't see.
"So yes, we were paying very close attention - but it's really just happened all of a sudden."
- APNZBy Matthew Backhouse @Mbackhouse Email Matthew