Ecuador's Cotopaxi volcano, located near the capital Quito, has exploded, sending clouds of steam and ash more than a kilometre above its rim.
Many residents had already evacuated last week but those who stayed behind were struggling to herd sheep and cattle to safety.
The explosions on Saturday morning inside the volcano were caused by magma meeting water.
The Security Coordinator Ministry said the volcano would continue to emit vapour with moderate amounts of ash.
The 5,987-metre volcano is one of the world's most feared due to its location just 50km from Quito.
The snow-capped volcano, which last had a major eruption in 1877, is close to heavily populated areas around Quito.
Last week, President Rafael Correa declared a state of emergency over the volcano's increasing activity.
The decree gave authorities more flexibility in using government funds to deal with any problems.
Dozens of families fled the immediate vicinity last week, setting up tents and improvised camps at a higher location, where they continued to watch the volcanic activity.
Authorities had already restricted access to the park that surrounds Cotopaxi and suspended ascents of the peak, which is popular with mountaineers.