QUITO, Ecuador – Ecuador’s Tungurahua volcano hurled truck-sized pyroclastic boulders more than a mile Friday in a powerful eruption that prompted at least 300 people to flee their homes, authorities said.

Schools were closed for a third straight day as ash showered down on a dozen towns in the sparsely populated area surrounding the 16,480-foot volcano.

Thundering explosions could be heard miles from Tungurahua, which is on the Andes cordillera 84 miles southeast of Ecuador’s capital, Quito.

A state Geophysics Institute scientist monitoring the volcano from a nearby observation post said by phone that incandescent boulders were landing up to 1.2 miles beneath crater level.

“The smallest blocks are that size of an automobile while the biggest reach the size of a truck, which cause impact craters up to 10 meters (33 feet) wide as they hit the flanks,” the scientist, Silvana Hidalgo, said. She called the eruption level “moderate to high.”

Civil defense officials reported an intense shower of ash east of the volcano, including in Banos, a tourist destination popular for its hot springs.

The volcano has been active since 1999. Eruptions in 2006 killed at least four people and forced thousands to flee.