Malacañang said it is closely monitoring the Bulusan Volcano in Sorsogon following its phreatic eruption Sunday morning.

A one-kilometer tall grey plume spewed from Mount Bulusan and prompted the Philippine Institute of Volcanology and Seismology (Phivolcs) to declare Alert Level One.

In a statement, Acting Presidential Spokesperson Martin Andanar said concerned government agencies were alerted.

"All concerned agencies are on standby 24/7 after Alert Level 1 has been raised," Andanar said.

Andanar reminded the public, particularly residents of surrounding areas, ''to be vigilant, monitor any development regarding the volcano’s condition and cooperate with local authorities.''

Ashfall was reported in the municipalities of Juban and Casiguran in Sorsogon. DMS