Airports at Palmerston North, Taupo, Napier and Rotorua were closed, as were roads linking Wellington and Auckland because of a large ash cloud that was thrown up into the air by the eruption at the 6490ft volcano.
“I saw this beautiful, big cloud and I thought ‘Gee, that looks like a volcanic plume,’” lorry driver Bryn Rodda told New Zealand National Radio.
“Just as I thought that there was a great big orange flash. It was quite impressive.”
Seismologists had recorded activity at the volcano, one of much volcanic activity over the coming weeks, months or even years.
The ash cloud is blowing eastwards towards the Pacific.
The volcano last erupted in 1897.