Mt Ruapehu could have a minor eruption within the next four weeks, according to volcanic monitor GNS Science.
Volcanic tremors and temperatures at Mt Ruapehu's Crater Lake, Te Wai ā-moe, have decreased in the past week.
But GNS Science reported gas emissions were still high and as volcanic unrest at Mt Ruapehu continues, the "potential for eruptive activity" remains the same.
GNS Science duty volcanologist Yannik Behr said the last gas measurement flight, on May 13, confirmed there were high levels of sulphur dioxide and carbon dioxide at the lake.
"Continued emission of sulphur dioxide [shows the] gas was released from shallow magma and suggests the volcano is still at a heightened level of unrest.
"Within the next four weeks, the most likely outcome of this unrest episode is minor eruptive activity that is confined to the lake basin, or no eruption."
Behr said minor eruptions may generate dangerous volcanic mudflows in the Whangaehu River.
According to Behr, the second most likely scenario would be a larger eruption.
"[A bigger eruption] could generate volcanic mudflows in multiple catchments like what was seen after the September 2007 eruption or older events like those in 1969."
Behr also said the chance of a larger eruption on the same scale as what happened in 1995-96 is higher than it was two months ago.
"But within the next four weeks [that kind of eruption] remains very unlikely.
"Mt Ruapehu is an active volcano and has the potential to erupt with little or no warning when in a state of elevated volcanic unrest."
Due to the heightened volcanic unrest, GNS Science staff are carrying out more-frequent aerial observations and gas measurements when the weather is suitable.