Updated satellite imagery of Home Reef displayed by Sentinel satellite. Photo: Tonga Geological Service
Tonga Geological Service is continuing to monitor the Home Reef submarine volcano after an ash plume drifting northeast was detected by satellite at 1.30am local time on 21 June.
The lastest public notice update issued on Sunday at 6pm local time said six thermal anomalies have been detected.
There is a low risk to Vava'u and Ha'apai communities.
Boaties have been told to keep a four kilometre distance from Home Reef until further notice.
An eruption in 1984 produced a 12-km-high eruption plume.
There was another island-forming eruption in 2006 which produced widespread pumice rafts that drifted as far as Australia.
The Tonga Geological Service reported that an intense thermal anomaly along the SE coast of Home Reef was identified in a 15 June.
Satellite image showed lava flowing E and expanding the coastline. Thermal anomalies continued to be detected during 16-17 June.
Home Reef is a submarine volcano located in the central Tonga islands between Lateiki (Metis Shoal) and Late Island.