The Hunga Tonga Hunga Ha'apai volcano continues to erupt intermittently, and ash has been detected in all directions up to 30km away.
The head of Tonga Geological Services, Taaniela Kula, said that the ash cloud had risen to heights of 12km and the direction of ash had varied with the wind conditions.
"On Tuesday, ash was drifting east but shifted directions last night to north east and has continued to drift in a northerly direction today," he said.
Overall, the amount of ash, steam and gas being spewed from the volcano has reduced, in comparison to last week, Kula said.
He noted that the volcano was about 60km away from uninhabited areas, and that no earthquakes had been detected on their seismometers.
This indicated that the magma chamber, which is feeding the eruption, is unlikely to be deeper than 7km below the ocean floor.
Currently the danger grade for the ash fall is orange, with red being the most severe. While no one has reported ash falling on houses yet, Kula advised that the public should take measures to protect their rainwater catchment and storage systems, should ash make landfall.
Kula said that people need to make sure they continue to sanitise and maintain their rainwater tanks, to stop the growth of a particular algae bloom that results from ash contamination.