MANILA, Philippines — Mt. Mayon, the country’s most active volcano, is rumbling and could erupt again soon, volcanologists warned Friday as they raised the alert level status around the 2,460-meter mountain from one (low-level unrest) to two (moderate unrest).

This means that the volcano is in a state of increasing unrest, which could lead to ash explosions and eventual eruption, the Philippine Institute of Volcanology and Seismology (Phivolcs) said in a bulletin issued early Friday.

Residents were reminded not to venture into a “permanent danger zone” in a six-kilometer radius from the volcano’s crater.

The zone was extended to seven kilometers on the volcano’s southeast flank because of the threat from sudden explosions and rockfalls.

Philvolcs also said that rivers and other areas that are lahar-prone in the southeast sector should also be avoided, particularly when there is heavy and prolonged rainfall.

The cone-shaped volcano in Albay province has been showing increased activity since June, and early this week volcanologists began closely monitoring Mayon when it began emitting steam and a strong glow at the summit crater could be seen with the naked eye.

Glow at crater

Phivolcs said the frequency of volcanic earthquakes on Mayon has increased. This could indicate the movement of magma below the surface that could lead to ash explosions and eventually to a hazardous magmatic eruption, it said.

The increased frequency of low-level volcanic quakes had pushed toward the crater lip, a cone-shaped pile of hot, steaming old rocks, possibly remnants from previous eruptions which could be the source of the glow at the crater, Phivolcs said.

Phivolcs said the present seismic count is at the same level as when a phreatic (steam-driven) explosion occurred in August 2008.

It said the glow at the summit crater has intensified and could now be observed from the Lignon Hill Observatory without the aid of telescopes.

Phivolcs Director Renato Solidum said the immediate danger if volcanic activity escalates was of ash explosions that could affect aviation at the Legazpi airport or crush roofs of nearby houses.

48 eruptions

Mayon has erupted 48 times since records began, most recently in 2006. A major eruption in 1814 buried the town of Cagsawa.

The volcano spewed ash and lava from July to October 2006, sending about 30,000 people away from homes.

Typhoon-triggered mudslides along Mayon’s slopes buried entire villages in December 2006, killing more than 1,000 people.

In a text message, Albay Gov. Joey Salceda said the province was preparing in the face of the alarming conditions of Mayon.

He said concerned agencies would start updating the data on the population at risk and critical resources of cities and municipalities around the volcano.

Regular bulletins

He said his people are working on the telecommunications companies to expedite the land line application for the Phivolcs observatory at Lignon Hill so regular bulletins can be released to media outfits.

“We also have to evaluate communication and warning capacities and maintain media relations and review contingency plans and update when necessary,” Salceda said.

Cedric Daep, director of the Albay Provincial Safety and Emergency Management Office (Apsemo), said the provincial government has been issuing official advisories based on the Phivolcs warnings.

He said the Apsemo was now in the process of assessing the population at risk to prepare them in case an evacuation is ordered. With Agence France-Presse and Associated Press reports