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 the Tauranga and Rotorua airports on Thursday morning after an eruption at Whakaari.

GNS Science is 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.

Air New Zealand says volcanic ash has been across the flight path for both airports.

At 11.30am, it says 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.”

Air Chathams says it will be monitoring conditions for flights to Whakatāne on Thursday afternoon due to volcanic activity at Whakaari/White Island.

Its chief commercial officer Duane Emeny says one of its aircraft was able to make a return trip to Whakatāne this morning.

GNS volcanic duty officer Brad Scott says the volcano has been in a state of minor eruption for several weeks now - but GNS is not aware of any significant change in the volcano’s activity.

Brad says experts were out near the island on Wednesday afternoon and saw ash falling within 1km of the volcano, with the plume drifting off to sea.

MetService meteorologist Mathapelo Makgabutlane says the wind direction has been mostly pushing ash away from the mainland but that was not the case overnight.

A northerly wind pushed ash towards the Eastern Bay of Plenty, and high levels of that ash start to pose a risk to aviation.

Mathapelo says MetService’s advisory centre is keeping an eye on this and is in communication with the aviation industry.

Ash cloud up to 1200 metres above sea level has been observed.

Emergency authorities say people on the mainland don't need to be concerned about the volcanic activity.

Bay of Plenty Emergency Management’s Lisa Glass says the volcano is going through an extended active period, but nothing particularly different was happening there today.

She says it's highly unlikely ash will reach the mainland.

Anyone out on the water should stay two nautical miles from the island.

* An earlier version of this story said black ash was washing up on Pāpāmoa Beach, it was not ash but a natural occurrence where sand has eroded.

-RNZ