The Philippine Institute of Volcanology and Seismology (Phivolcs) detected 26 earthquakes in Mt. Kanlaon and 10 quakes in Mt. Pinatubo in the past 24 hours, as both active volcanoes remained under Alert Level 1 due to "abnormal" conditions.

The agency on Wednesday, April 28, said it observed a weak to moderate emission of white steam-laden plumes that rose 400 meters before drifting southwest and northwest at Mt. Kanlaon.

Sulfur dioxide emission was measured at an average of 1,022 tonnes per day last Sunday, April 25.

Likewise, Phivolcs noted that ground deformation data from continuous GPS and electronic tilt measurements have been recording slight inflation of the lower and middle slopes since June 2020.

"These parameters may indicate hydrothermal, tectonic, or deep-seated magmatic processes occurring deep beneath the edifice," it said.

Phivolcs reiterated that Mt. Kanlaon is still under Alert Level 1, which means that it is in abnormal condition and period of unrest.

It reminded the public not to enter the four-kilometer radius permanent danger zone due to further possibilities of sudden and hazardous steam-driven or phreatic eruptions.

Civil aviation authorities were also asked to advise pilots to avoid flying close to Mt. Kanlaon's summit as ejecta from any sudden phreatic eruption can be hazardous to aircraft.

Likewise, Phivolcs said Alert Level 1 still prevails over Mt. Pinatubo due to "low-level unrest that may be related to tectonic processes beneath its edifice."

However, it said that "no imminent eruption is foreseen."

"Entry into the Pinatubo Crater area must be conducted with extreme caution and should be avoided if possible," it advised.

Communities and local government units surrounding Pinatubo were reminded to remain prepared for both earthquake and volcanic hazards and to review, prepare and strengthen their contingency, emergency, and other disaster preparedness plans.