New up-close video of Whakaari/White Island has been released after its recent rumblings.
Minor eruptions started on Friday morning, with a steam and gas plume rising to more than 2km.
There were two eruptions on Saturday.
Scientists think the island, which erupted with deadly force in late 2019, could be going into what's known as an eruptive episode.
GNS earlier said while there are no clear signs eruptions will get bigger, they could do so with little or no warning.
Sensors on the island have been degrading and going offline since the 2019 eruption, meaning scientists have had to rely on webcams and satellite images.
That was until today, when GNS staff were able to fly in a plane over the island with scientific instruments.
GNS volcanologist Geoff Kilgour told 1News it gives a more detailed look at what's happening than a helicopter flight on Friday.
It could also fly through the plume, which a helicopter was unable to do.
"The helicopter allows us to open the door. We can get a thermal camera, as well as taking really steady clear video and still photos.
"Today was the plane because that's what we use to measure the gases that are coming out of the volcano," he explained.
He said today's video was able to show the dynamics of the volcano's vent area and the steam being emitted.
"And I think that's a great insight into what's happening at the volcano right now."
As for what is happening, Kilgour said there were a couple of things learnt today — activity today was a little lower than what it was on Friday.
"But also the key thing that we were able to see today because we had really really good views into the crater area is that we don't see huge evidence, or any evidence, for material that was erupted out during either Friday or Saturday," he said.
"And so what we think has happened is there's been really quite intense gas emissions but not a very explosive phase which has broken up rocks and then flown them around the crater floor, so it means the activity we've been seeing is actually very, very minor and actually only barely detectable."
The gas readings taken from Monday's flight will start to be analysed on Tuesday.
They will then be used to help decide what happens with Whakaari's volcanic alert level.
"It samples the emissions coming from the volcano and that really does help us understand what could happen next."
"So over the next day or so we'll start to understand what the gas emissions were and therefore what could be the most likely pathway forward," Kilgour said.
Late today, GNS formally issued an advisory saying the volcanic alert level would remain at 3.
The statement said the lake level is lower than before the recent activity, with the lake progressively changing to a grey colour.
"Based on our limited information there have been no clear indications of the current volcanic episode intensifying or declining," GNS said.
An eruption of the volcano in 2019 killed 22 people and injured 25 others.
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