WELLINGTON, New Zealand — New Zealand and Australia have sent military surveillance flights to assess the damage in Tonga caused by Saturday's huge undersea volcanic eruption.

Communications with the Pacific island nation have remained limited since the eruption. The blast likely severed the single underwater cable that provides internet and international phone service.

No casualties have been confirmed on Tonga, although a British woman is reported missing. Officials in nearby countries have warned that casualty numbers could skyrocket once communication is re-established.

"Communication with Tonga remains very limited. And I know that is causing a huge amount of anxiety for the Tongan community here," New Zealand Prime Minister Jacinda Ardern said.

Residents who got messages out to the world described a moonscape left by tsunami waves and volcanic ash fall.

The ash was contaminating drinking water, and New Zealand is planning to fly water and other supplies to Tonga on Tuesday.

According to CNN, the blast on Saturday was likely the most violent eruption the world has seen in three decades. Following the explosion, tsunami advisories briefly went out across the Pacific Rim from Japan to Southern California to South America.

"The eruption was very powerful. There are reports it was heard as far as Alaska," Wendy K. Stovall, a member of the USGS Volcano Hazards Program, told KPIX-TV in San Francisco.