According to news articles the Tonga Geological Services Office of the Ministry of Lands and Natural Resources stated that several observations indicating a possible eruption at Metis Shoal, also known as Lateiki, were reported during 13-15 October.
Real Tonga pilots flying between Tongatapu and Vava'u observed the intermittent plumes rising to 4.6-5.2 km (15,000-17,000 ft) a.s.l.
and drifting N on 15 October.
Ash in the plumes was not identifiable according to the Wellington VAAC.
Sources: Matangi Tonga Online ,Matangi Tonga Online ,Wellington Volcanic Ash Advisory Center (VAAC)