prompted a potential threat warning to be issued for much of central North Island, New Zealand.
The volcanic activity occurred on Monday, on the northern side of the mountain, near the Te Mari Craters.
In the first eruption for more than a century, a thick ash cloud is covering much of central North Island. Witnesses have reported seeing "flame-like explosions", red hot rocks being thrown into the air, lightning, and they heard loud explosions.
reports state that the volcanic alert level has risen from 1 to 2, and the aviation color code has been raised to red.
Civil Defense warned the eruption could pose a threat to the Waikato, Hawkes Bay, Gisborne, Manawatu-Wanganui, Bay of Plenty and Taranaki regions.
Flights are likely to be disrupted and roads are closed. Residents living nearby have been advised to stay indoors, as rock and ash is spewing from the mountain.
Volcanic ash on the road.