One of Indonesia’s most dangerous volcanoes shot a plume of ash and sand over half a mile into the sky forcing hundreds of villagers to flee into the night.

Mount Merapi, located near Yogyakarta, produced a short but massive rumbling before dawn Monday and spewed the ash cloud for hours. The ash fell as far as 8.5 miles from the volcano before activity ceased Monday afternoon.

“This was not an eruption, just the sliding-down of volcanic material from the top of the volcano,” said Agus Hendratno of Gadjah Mada University in Yogyakarta. He said the ash plume indicates a collapse of part of the volcano’s lava dome.

A spokesman for the country’s disaster agency said the alert level for the volcano remains normal but they will continue to monitor for a potential lava eruption. The country’s most seismically active volcano, Mount Merapi erupted in 2010 releasing poison gas killing more than 300 people.

Indonesia is located on the Pacific Ring of Fire.