The so-called Volcano of Fire was spitting hot ash thousands of meters into the air, the National Volcanology Institute said.
Avid de Leon of the National Disaster Reduction Coordinator body told reporters 300 people were evacuated as a precaution from the village of Panimache.
The village lies near the foot of the 3,763-meter (12,345-foot) volcano, some 35 kilometers southwest of the capital.
Ten schools in the southern Escuintla district suspended classes due to falling ash.
A major eruption of the volcano in February 2015 forced the capital's main airport to be closed.