Delia Tubianosa, resident volcanologist at Bulusan’s Cabid-An monitoring station here, however, belied earlier reports that Bulusan exploded last Monday.
Tubianosa said the ashfalls in the towns of Irosin, Juban and Casiguran were triggered not by an ash explosion but by the volcano’s voluminous or heavy steaming that has agitated the ash deposits on the crater wall.
She said the Philippine Institute of Volcanology and Seismology is closely watching the volcano since its heavy steaming might trigger ash explosions.
"Since Bulusan remains abnormal, it is always possible that this steaming would shift to ash explosions," she said.
Tubianosa said the last ash explosion occurred on Jan. 26 this year, sending mild ash deposits to Irosin, Casiguran and Juban towns.
In April last year, at least 5,000 villagers were ordered evacuated after a series of ash explosions as high as five kilometers above the volcano’s crater.
Bulusan is the second most active volcano in Bicol, next to the cone-shaped Mayon Volcano in Albay. Last Nov. 30, heavy rains spawned by typhoon "Reming" triggered mudflows from the slopes of Mayon, burying several villages and killing at least 1,500 people.