A volcano began spewing ash Saturday for the first time in 600 years, and U.S. authorities planned an evacuation of nearby Clark Air Base if volcanic activity increased. Mount Pinatubo, a 4,795-foot volcano about 60 miles northwest of Manila, sent steam 16,000 feet into the air and sent ash as far as 15 miles away, officials said.
More than 3,100 people, mostly members of the Aeta tribe, have been evacuated from the mountain's slopes.
At the U.S. air base, about 10 miles southeast of the volcano, Air Force spokesman Lt. Col. Ron Rand said contingency evacuation plans had been prepared. The 16,000 troops, Defense Department civilians and dependents would be moved to the U.S.-run Subic Bay naval base, about 30 miles southwest of Clark.
Rand did not say if the evacuation plan would be carried out.
"The chance of an eruption has greatly increased," said Delfin Garcia of the Philippine Institute of Volcanology and Seismology.
Mount Pinatubo began showing signs of seismic activity in April. It has not erupted since the 14th century.