Philippine scientists raised the alert level on a restive volcano Sunday after detecting increasing signs of activity that could be a precursor to a new bout of explosive eruptions, officials said. The 1,560-meter (5,149-foot) Mount Bulusan in Sorsogon province, about 390 kilometers (240 miles) southeast of Manila, has been showing signs of unrest since coming back to life in March 2006 with on-and-off ash and steam explosions, The Associated Press reported. Since it ejected ash on May 12, the mountain's northeastern slope has swelled slightly and abnormally high numbers of earthquakes have been recorded, prompting authorities on Sunday to raise the public alert level from one to two on a five-step scale, the Philippine Institute of Volcanology and Seismology said in a statement. The alert upgrade indicates a shift from «low-level volcanic activity» to a «moderate level of volcanic unrest,» said Crispulo Diolata, an official at the institute. An alert level of five means a life-threatening eruption is in progress, Diolata said. «The high level of seismic activity and the observed inflation indicate increasing volcanic unrest,» the institute said in its statement. «The current activity may lead to more explosive eruptions.» Villagers were warned not to venture into a four-kilometer (2.5-mile) «permanent danger zone» around the volcano. The Philippine archipelago lies on the Pacific Ocean's «Ring of Fire,» where volcanic activity and earthquakes are common. In December, typhoon-triggered mudslides along the slopes of nearby Mayon volcano buried entire villages, killing more than 1,000 people.
