The Hunga Tonga Hunga Ha'apai volcano in Tonga is continuing to pump plumes of gas and dust several kilometres in to the air.

RNZ Pacific correspondent Kalafi Moala said there seemed to be no end to the eruption, with another one occurring on Thursday.

"With the wind conditions it has affected mostly the Ha'apai area but also Vava'u and it's not affecting Tongatapu even thoguh we in Nuku'alofa can actually see it taking place. Yesterday (Wednesday) I was driving by and looked out at the waterfront and I saw lightning coming out of the area," he said.

An Air New Zealand flight had to turn back mid-flight on Tuesday.

The body of Lord Ma'afu was on that flight and the delay has resulted in his funeral in Tonga being postponed.

Monitoring the eruption

Tonga's geology team is working 24/7 monitoring the Hunga Tonga Hunga Haapai eruption.

Lead geologist Taniela Kula said Tonga's navy got within four kilometres of the eruption site to record the erruption.

Visual recording had helped confirms it was the same source as the last eruption there seven years ago, Kula said.

"It showed a really explosive eruption spewing out materials up 350 metres above sea level just over the vent."

Steam clouds from the eruption were reaching 14 kilometres above sea level and are drifting north-north-east towards Samoa, Kula said.

Hunga Tonga Hunga Haapai last erupted in 2014 and before that in 2009.

"This morning (Thursday) we noticed a slow reduction in the amount of gas emitted from Hunga Tonga Hunga Ha'apai but it's still continuously erupting, but at a lower pace than yesterday.

"It's a natural phenomena and we can only observe what comes out of it - [there is] not enough equipment to probe into what's in the sub-surface of the volcano," he said.