An outing turned into terror for a group of school children visiting Mount Tongariro today.
Ninety children and eight adults from Napier's Tamatea Intermediate were eating their lunch when the Te Maari crater erupted about 1.25pm.
The "shaken" children, rushed back to the school bus which was waiting for them at the end of the track.
Amateur video shows the children running down the track, some screaming, as an ominous black cloud of ash rises behind them.
"It was a very exciting day, not quite the day we had planned," said Principal Roy Sye. "They are studying volcanoes, so they got a first-hand look at when nature goes unannounced."
The school's outing was their second trip to the volatile region in the last two weeks.
"We looked at the DOC warnings and advisories, and we do make sure we ring and check on the day for any heightened level of risk," Sye said.
Twenty students and eleven staff from Auckland's Gulf Harbour School also made their way safely back down the mountain.
Sam Kennedy was one of 50 trampers on the Tongariro Alpine Crossing when the eruption occurred.
"It was completely silent. It was just really eerie and surreal," he said.
Earlier, Greg Hooper from Tongariro Holiday Park told ONE News that he saw a haze in the distance, and lots of cloud cover.
Hooper said he knew of 40 Holiday Park guests who were visiting the mountain, but received confirmation soon after the eruption from members of the group that they were all safe and sound.
Scientists cannot rule out that today's eruption is linked to recent volcanic activity on Mount Ruapehu.
"We were not expecting this. The stuff at Ruapehu think there's no link, but maybe there is, maybe we don't understand it well enough," said volcanologist Steve Sherburn.
"We may see several more rumbles over the next few days but because nothing told us this was coming, it was very hard to look forward and say we've seen this, therefore there must be another eruption, so I guess we're like everybody - on the edge of our seats," he said.
Meanwhile, the Civil Aviation Authority is monitoring the spread of the ash cloud.
"The eruption has extended to about 15,000 feet and the plume will spread out over the central plateau over the next twelve hours or so and then it will dissipate over the next few days," said Civil Aviation Authority's Peter Lechner.
Civil defence has issued a warning that an ash cloud could be looming over the central North Island from Waikato to the Hawke's Bay for several days.