A total of 104 earthquakes were recorded on Kanlaon Volcano in Negros Island during the last 24-hour observation period, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said Tuesday.

In its 8 a.m. advisory, PHIVOLCS said one such seismic activity happened at 5:07 a.m. on Monday at magnitude 3, and intensity 2 was felt in La Carlota City, Negros Occidental.

“DOST-PHIVOLCS would like to remind the public that Kanlaon Volcano is at Alert Level 1 which means that it is at an abnormal condition and has entered a period of unrest,” the advisory said.

• White steam, 136 quakes observed in Kanlaon Volcano in Negros

The volcano’s vent showed weak emission of white steam-laden plumes that rose 300 meters before drifting northwest and southeast. Sulfur dioxide emission was measured at an average of 438 tons/day on June 13.

Since January, lower and mid slopes showed slight deflation. Electronic tilt monitoring on the southeastern flanks also recorded continuing deflation on the lower slopes but inflation on mid slopes since April, said PHIVOLCS.

“These parameters indicate that hydrothermal and magmatic activity is occurring beneath the edifice,” it said.

The state volcanology agency said entry to the 4-kilometer radius permanent danger zone must be strictly prohibited due to possible sudden and hazardous steam-driven or phreatic eruptions.

Civil aviation authorities must also advise pilots to avoid flying close to the volcano’s summit as ejected from any sudden phreatic eruption can be hazardous to aircraft.