Phreatic eruption at Bulusan volcano at 2:40PM. Grayish to dirty white eruption plume reached 2,000 meters above summit | via @phivolcs_dost pic.twitter.com/baj8kFsgsT

— ABS-CBN News (@ABSCBNNews) December 29, 2016

MANILA - Mt. Bulusan in Sorsogon, Bicol had a phreatic eruption Thursday, launching a plume of ash about two kilometers high.

The Philippine Institute of Volcanology (Phivolcs) said the explosion was "recorded as an explosion-type earthquake" that lasted 16 minutes from 2:40 p.m.

The 2,000-meter, white-to-grayish ash plume drifted west northwest, Phivolcs added.

Before this, Bulusan generated a seismic earthquake in the last 24 hours and showed increased seismic activity between December 22 and 29.

Alert Level 1, indicating abnormal activity, remains over Bulusan, state seismologists said.

This indicates that hydrothermal processes are underway beneath the volcano, which may lead to more steam-driven eruptions.

Phivolvs also reminded the public not to enter the 4-kilometer radius Permanent Danger Zone (PDZ).

Residents within valleys and along river or stream channels southwest and northwest of the volcano were also reminded to guard against sediment-laden stream flows and lahar in the event of heavy and prolonged rainfall.

Pilots have also been asked to steer clear of the volcano’s summit to avoid ash from any sudden explosions.

Phivolcs said it will continue to monitor volcanic activity.