Around twenty scientists are now on the ground in the Tongariro region, hoping to determine the exact cause of last night's eruption.
GNS Science reports that although Mount Tongariro has been dormant for the past 115 years, it has been showing signs of waking over the past two weeks.
Volcanologist Graham Leonard says that in the past week there have been multiple alert bulletins indicating earthquake and gas activity.
As the eruption forced a plume of ash cloud into the sky - suggesting that the eruption was steam driven - GNS scientists are now working to determine the exact cause.
"It's either been an explosion in that hydrothermal system right up near the surface or some more direct input from the magma a bit further down and we're looking into that now," Leonard told ONE News.
Tongariro last erupted in 1897, although Ngauruhoe - geologically considered a vent of Tongariro - blew in 1974-75.
Teams of scientists have dispersed today to collect ash samples from the area, but while the weather hampered their efforts today, MetService expects the conditions to improve tomorrow.
Civil Aviation Authority Meteorologist Peter Lechner said that, "providing no further eruptions their shouldn't be any further ash problems as the low pressure moves over the country it will only push the existing ash cloud further into the southern ocean.".
Professor Colin Wilson, a volcanologist from Victoria University says that Tongariro first evolved around 350,000 years ago and has been sporadically active and building ever since.
Mount Tongariro is part of the Taupo volcanic zone, which includes Mount Ruapehu and the nation's most active volcano - White Island.
Wilson says that the eruption appears to be similar to those in the 1890s, but this does not signal the potential for a much larger one.
"It would require the volcano to behave in a style that it hasn't behaved in for the order of ten thousand years or more," Wilson said.