In a bulletin on early Sunday, the Philippine Institute of Volcanology and Seismology (Philvolcs) raised the alert status of the Mayon volcano one notch to level 2, which means the current activity is "probably of magmatic origin, which could lead to more phreatic eruptions or eventually to hazardous magmatic eruptions".
Saturday's eruption unleashed ash, rocks and sulfuric odor, and was followed by rumbling sounds and a faint glow in the crater, according to Phivolcs.
Prior to this phreatic eruption, Mayon's edifice has undergone inflationary changes or a slight swelling of the edifice as indicated by ground deformation data recorded by continuous Global Positioning System and tilt since October and November 2017, respectively.
A second ash eruption was also recorded before noon on Sunday.
The Mayon Volcano once again spewed "ash plume" at 11:43 a.m that lasted for about 15 minutes based on seismic record, Phivolcs said in its 3:30 p.m. advisory.
Mayon, known as the Fuji of the Philippines due to its near-perfect cone shape, had "phreatic or steam-driven eruption" yesterday (Saturday, January 13) and there was a further eruption today.
A motorised tricycle speeding past the Mayon volcano
It last erupted in 2014, spewing lava and forcing thousands of people to evacuate.
The volcano's most destructive eruption took place in February 1841 when lava covered a nearby town and killed 1,200 people.
It also said that the 6-kilometer (km) permanent danger zone around the volcano, as well as the 7-km extended danger zone, should be enforced "due to the danger of rockfalls, landslides, and sudden explosions or dome collapse that may generate hazardous volcanic flows".
Phivolcs chief Renato Solidum said the volcano may be due for an eruption as it had been displaying abnormal behaviour for several month.
"It is hard today for us to collect data, especially ashes because of heavy rains", Daep said. In case of ash fall events, which are most likely to affect communities on the western and southwestern flanks downwind of Mayon's crater, people should cover their nose and mouth with damp, clean cloth or dust mask.