GNS says Mt Tongariro is still emitting sulphurous gas but has stopped spewing ash, and volcanic activity remains low after yesterday's eruption.
The smell from the volcano has been noticed in Manawatu and Hawke's Bay, the areas downwind from the Te Maari crater.
Scientists say the smell may be noticed up to 100km away from the volcano, and could cause minor irritation to people's eyes, skin and throats.
GNS Science is closely monitoring the activity at the volcano following its eruption, and will be looking to see if the temperature from gas samples increases.
Further similar eruptions are expected in the coming weeks.
"The volcano is in a state of unrest and in that state it can erupt, and it can erupt without any warning," volcanologist Brad Scott told ONE News.
"That unrest is going to continue for many weeks many months."
Scott said an eruption at Mount Tongariro on August 6 was "vent clearing" because the vent was blocked "so that was naturally more explosive".
"Now we've got a more open vent environment that makes it easier for eruptions to occur we can't get such high overpressure and therefore the explosions won't be as explosive or as large as August."
A team from GNS flew over the volcano this afternoon and said the eruption has caused no significant change to the crater.
The Volcanic Alert Level remains at 2 and the Aviation Colour Code at Orange.
Scientists are not the only ones monitoring Tongariro, a number of tourists have travelled to Tongariro eager to see what might happen. Police are advising them to put their safety first.
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