An eruption on Whakaari/White Island is causing flight delays.

At least 10 flights were cancelled and three delayed from both Tauranga and Rotorua Airports Thursday morning after an eruption at Whakaari.

GNS was currently investigating.

It said last week a new vent detected on Whakaari/White Island, which has been experiencing a minor eruption, was emitting an increase in volcanic ash.

Images showed the column of ash emitted from Whakaari growing considerably in size in the two hours to 8am.

Air New Zealand said volcanic ash was across the flight path for both airports.

It said it would continue to monitor the ash cloud, and said any other customers on flights should keep an eye on the Air NZ app in case there were other routes affected.

Air New Zealand's chief operational integrity and safety officer Captain David Morgan said the airline was continuing to monitor the movement of the ash.

"The safety of our people and our customers is our utmost priority."

Main image (RNZ/GNS Science): Increasing volcanic ash has been coming from Whakaari/White Island.