A new report from GNS Science says Mt Ruapehu is experiencing among the highest levels of volcanic tremors seen in the past nine years.
It comes after the alert level for the volcano was recently raised from 1 to 2 following "elevated volcanic unrest".
READ MORE: Mt Ruapehu alert level raised amid 'elevated volcanic unrest'
GNS Science volcanologist Yannik Behr said the temperature at Mt Ruapehu's crater lake had risen four degrees in the last eight days to 36 degrees Celsius.
"Volcanic tremor levels remain elevated and, after a slight increase over the past week, are now amongst the highest levels we have seen over the past nine years," Behr said.
Professor Phil Shane says the raising of the volcano's alert level doesn't necessarily mean there will be an eruption. (Source: 1News)
Analysis of lake water and gas samples does not indicate significant changes in the geothermal system feeding into the lake.
GeoNet data shows an increased number of earthquakes have occurred in the past few days as compared to the fortnight before.
"The results to date are typical for the beginning of a heating cycle with the exception that tremor values are unusually high," Behr said in his report.
"Current data indicate that normal processes seen at the crater lake are occurring."
Hazards associated with volcanic unrest at level 2 include steam discharge, volcanic gas, earthquakes, landslides and hydrothermal activity.
GeoNet warns volcanic eruptions can sometimes happen with no warning, regardless of alert level.
Two weeks ago, Professor Phil Shane, an Auckland University geologist, said the recent increase in volcanic activity at Ruapehu wasn’t necessarily cause for concern.
READ MORE: 'Watch this space' for signs of Ruapehu eruption - geologist
That includes an increase in the temperature at the lake at the top of the volcano and in the small earthquakes, or tremors, beneath it.
“It’s not definite evidence that that will happen but it’s the sort of thing we look for so that we can be prepared for these types of eruption events in the future,” Shane said.
“Any change in the alert level is significant but we do need to remember that some of the activity at Ruapehu is cyclic.”
He compared the increased seismic activity to the volcano “clearing its throat” and says it’s a case of waiting to see if that continues.
Mt Ruapehu hasn't erupted since 2007, when ash, mud and rocks were blasted skyward. No one died, although two climbers were caught in the eruption in a hut just 600m from the crater lake, with one having to be rescued after becoming trapped.
The last major eruptions occurred in 1995 and 1996. The first of those in June 1995 was preceded by the crater lake heating to 50 degrees Celsius in January of the same year.
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