Mount Pinatubo spewed a cloud of ash and gas more than 15 1/2 miles high Thursday after a turbulent night in which the volcano shook with the most intense fury since it awoke from six centuries of sleep.
"What we are seeing now are phenomenal eruptions," said Raymundo Punongbayan, director of the Philippine Institute of Volcanology and Seismology. "The story of Mount Pinatubo is not quite over yet.""This is already the big bang," Punongbayan said.
Two deaths have been reported from the eruptions, which began Sunday.
A Filipino serving in the U.S. Navy was killed Wednesday when his car skidded on an ash-slickened road north of the Subic Bay Naval Base, about 30 miles southwest of the volcano, and crashed into a bus.
A member of the Aeta tribe that lives on the slopes of Pinatubo, said he saw his uncle die in an eruption Wednesday. There was no official confirmation, but the man himself was badly burned.
The latest eruption occurred at 8:41 a.m. Thursday and lasted for a half hour. It unleashed giant mudflows down the jagged, ash-covered western slopes of the 4,795-foot mountain and into the Marella River.
The eruption sent a gray avalanche of deadly ash, gases and molten rock down the slopes. The billowing ash cloud above turned day to dusk.
Associated Press reporter Claro Cortes, who was 10 miles west of the crater when the eruption occurred, said residents fled on foot in panic, some clutching chickens and holding handkerchiefs before their faces.
About 40 reporters and photographers ran for their cars, taking in as many residents as they could.
Aviation authorities warned airline pilots to avoid flying near the volcano after a Saudi Airlines 747 developed engine trouble Wednesday when it passed near the ash cloud en route to Manila from Dhahran.
After the nighttime eruptions, the troops that remained at nearby Clark Air Base, from which most personnel were evacuated on Monday, prepared to evacuate.