Officials will travel from Tonga on Friday to the site of a underwater volcano which has sent plumes of steam and smoke 1000 metres into the sky.
The volcano is about 3km west of the main island of Tongatapu.
Chief geologist Kelepi Mafi says the smoke was visible on Monday.
While there appears to have been no impact on the island, officials will go to the site by boat on Friday to assess the area.
Mr Mafi says fisherman have been told to stay away from the area.