Mount Tongariro has erupted, GNS Science reports.
The eruption came from Te Maari Crater, on the western side of the mountain, shortly before 1.30pm.
A massive plume of ash can be seen coming from the mountain.
GNS Science duty volcanologist Nico Fournier told APNZ the eruption happened about 1.20pm.
"There was one eruption, essentially one explosion, and it was not sustained. It spewed some ash possibly a couple of kilometres up the air. The ash is now drifting to the east-southeast.''