The explosion and lava emission confirmed the continuous ascent of magma into the volcano’s crater, and the Philippine Institute of Volcanology and Seismology (Phivolcs) might raise the alert level from 3 to 4 if Mayon’s abnormal behavior worsens.
"The magma is now very close to the crater," said volcanologist Alex Baloloy.
But he said the volcano will not erupt soon, adding that raising the alert level will take into consideration other parameters like the sulfur dioxide level, ground inflation, the number of volcanic quakes and lava trickles.
The explosion was recorded at about 6:42 p.m. Saturday, triggering the lava spill. Crater glow was observed between 7:50 p.m. and 8:12 p.m., and from 8:44 p.m. to midnight; as well as from 1:40 a.m. to 2:28 a.m. yesterday.
The upward movement of magma also caused rock falls at about 9:02 a.m. yesterday.
Last Friday, Mayon exploded at about 5:52 p.m., sending ash clouds some 50 meters into the air.
Seismic sensors around the volcano detected eight low-frequency and seven high-frequency volcanic quakes.
As soon as alert level 4 is raised, Phivolcs will immediately recommend the evacuation of residents from the six-kilometer permanent danger zone.
Taking no chances, the Commission on Elections has approved the request of Camalig election officer Faviola Melgar to transfer the polling precincts of four threatened barangays in Camalig town  Anoling, Quirangay, Tumpa and Sua, which have a total of 6,451 registered voters  to Tagaytay and Barangay 1.
Mayon last erupted in February last year.