LEGAZPI CITY, Philippines - The Philippine Institute of Volcanology and Seismology (Phivolcs) is considering raising the alert level on Mayon Volcano to 3 for its "high unrest" and increasing tendency towards eruption.

Volcanologists said they have observed intensified unrest in Mayon Volcano since early this week.

Mayon is now on alert level two, which means it is on moderate unrest.

The recent episode of three successive ash puffs prompted Albay Gov. Joey Salceda, also Provincial Disaster Coordinating Council chair, to advise the local disaster councils to remain vigilant in order to avoid deaths during an eruption and the evacuation of 30,000 residents in the path of pyroclastic flows.

Resident volcanologist Eduardo Laguerta and Alex Baloloy, senior science research analyst, went out to monitor sulfur dioxide emissions with the use of a fly spectrometer and to confirm reports from residents of Barangay (Village) Matanag here about foul odor, similar to that of rotten eggs, believed to have been caused by gas.

The scientists took advantage of the good weather condition and particularly focused on quakes, crater glow and the gas emissions that might provide enough basis for raising the alert.

The Mayon observatory center at the Liñgon Hill in Daraga, Albay recorded gas emission of 934 tons per day during the last 24-hour period (Sept. 16) from 682 tons on Sept. 15, barely 50 tons last Sept. 14 and 405 tons last Sept. 13.

A total of eight low frequency volcanic quakes and four high frequency quakes were recorded during the 24-hour observation period.