While they've only experienced small tidal surges and a light covering of ash, those in the northern Tonga island group Vava'u are largely cut off, the co-owner of a boatyard there says.
Joe Caesar, who lives in Mangawhai north of Auckland, has been in contact with his colleagues in Tonga via satellite text phone.
Many in the Vava'u island group, with a population of around 14,000, are unaware of the full extent of the damage elsewhere in the country with communication lines still down.
Caesar says he's been providing information to those in Vava'u based on what he's hearing back in New Zealand.
"They have pretty much zero contact with the outside world."
He's hearing concerns about crucial deliveries via ferry from the capital to the outer islands.
"The ferries provide general supplies, all food goods come up from Nuku'alofa, they're concerned about money, the bank system [if it's] working," he said.
"The ash cloud didn't quite reach Vava'u which is a bit of a relief," he told 1News on Monday.
Tsunami activity was also negligible compared to what was seen in Nuku'alofa, he said.
"The wave didn't have very much impact at all, it sounds like they had big tidal fluctuations."
The boatyard in Vava'u has been getting calls from Tongans in the United States, Australia and New Zealand who are concerned about their loved ones.
"We still trust that, even though we haven't heard from them for almost 24 hours now, but we believe and have hope that something good is going to come out from this," Reverend Vaka Taimani pastor of the First Tongan Assembly of God Church in San Carlos, California told ABC News.
"Just kept on praying because that's our hope."
A New Zealand Defence Force reconnaissance flight that was assessing the region is due back in Whenuapai on Monday evening.