The growing cloud as captured by GNZ cameras at Te Kaha at 8am on Thursday. Photo: GNS
*An earlier version of this story said black ash was washing up on Papamoa Beach, it was not ash but a natural occurrence where sand has eroded.
Flights in and out of Tauranga have resumed after volcanic ash from Whakaari/White Island caused problems.
At least 10 flights were cancelled and three delayed from both Tauranga and Rotorua Airports Thursday morning after an eruption at Whakaari.
GNS Science 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 smoke emitted from Whakaari growing considerably in size in the two hours to 8am.
Air New Zealand said volcanic ash had been across the flight path for both airports.
At 11.30am, it said flights had resumed and are operating as normal in and out of Tauranga.
"We are continuing to monitor the situation to determine whether any further flights in or out of Rotorua will be impacted and advise customers travelling today to check the Air NZ app or our website for the latest information on their flight.
The decision to cancel or delay flights this morning was a proactive safety measure."
Increasing volcanic ash has been coming from Whakaari/White Island. Photo: Supplied / GNS Science
Air Chathams said it would be monitoring conditions for flights to Whakatāne on Thursday afternoon due to volcanic activity at Whakaari / White Island.
Its chief commercial officer Duane Emeny said one of its aircrafts was able to make a return trip to Whakatāne this morning.
Emissions from Whaakari / White Island increasing in size from 6.20am (bottom right) to 8.10am (top left) on Thursday morning. Photo: GNS
GNS volcanic duty officer Brad Scott said the volcano had been in a state of minor eruption for several weeks now - but it was not aware of a significant change in the volcano's activity.
Scott said experts were out near the volcano on Wednesday afternoon and saw ash falling within one kilometre of the volcano, with the plume drifting off to sea.
MetService meteorologist Mathapelo Makgabutlane said the wind direction had been mostly pushing ash away from the mainland but that was not the case overnight.
A northerly wind saw ash pushed towards the eastern Bay of Plenty, and high levels of that ask start to pose a risk to aviation.
Makgabutlane said its advisory centre kept an eye on this and was in communication with the aviation industry.
Ash cloud up to 1200 metres above sea level was observed.
Emergency authorities said people on the mainland do not need to be concerned about the volcanic activity.
Bay of Plenty Emergency Management's Lisa Glass said the volcano is going through an extended active period, but there was nothing particularly different happening there today.
She said it was incredibly unlikely that ash would reach the mainland.
Anyone out on the water should stay two nautical miles from the island.