MANILA, Philippines — Authorities raised the alert status of Bulusan Volcano in Sorsogon to Alert Level 1 (Low-level Unrest) on Monday, following a phreatic eruption early morning that sent ash and pyroclastic material into nearby communities.

The Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported that the eruption occurred at 4:36 a.m. and lasted for 24 minutes, producing a bent ash plume that rose 4,500 meters above the summit crater before drifting west to southwest.

Ashfall was reported in Barangays Cogon and Bolos in Irosin, and Barangays Puting Sapa, Guruyan, Buraburan, and Tulatula Sur in Juban, all in Sorsogon province. A pyroclastic density current (PDC) or “uson” also flowed down the southwestern slopes of the volcano, reaching up to three kilometers from the summit.

Prior to the eruption, PHIVOLCS recorded 53 volcanic earthquakes within a 24-hour period. Local officials also reported hearing rumbling sounds approximately 15 minutes before the eruption, which were detected by infrasound sensors.

PHIVOLCS warned that succeeding phreatic eruptions could occur and urged local government units and the public to strictly avoid the four-kilometer Permanent Danger Zone (PDZ) around the volcano. Increased caution is also advised within the two-kilometer Extended Danger Zone (EDZ) on the southeast sector.

Communities affected by ashfall were advised to use protective masks or wet cloths to prevent inhalation of volcanic ash. Civil aviation authorities were also alerted to advise pilots against flying near Bulusan’s summit due to the risks posed by sudden ash emissions.

Residents living along valleys and river channels, particularly on the volcano’s southeast, southwest, and northwest sectors, were also warned of potential lahar flows should heavy rains coincide with volcanic activity.

PHIVOLCS said it continues to monitor Bulusan Volcano closely and will issue updates as necessary.