At least six people were dead after Guatemala's Fuego volcano erupted Sunday, authorities said.
Leading officials fear the toll could rise.
About four hours later, lava began flowing down the side of the mountain.
Video images show a charred landscape where a lava flow came into contact with homes.
The volcano is located some 25 miles south-west of Guatemala City and has been spewing smoke and ash.
Hundreds of rescue workers, including firefighters, police and soldiers worked to recover bodies from the still-smoking lava.
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Guatemala's national disaster coordinator, Sergio Cabañas, said an undetermined number of people were missing following the eruption of the Volcán de Fuego, about 30 miles from Guatemala City.
"Unfortunately El Rodeo was buried and we haven't been able to reach the La Libertad village because of the lava and maybe there are people that died there too", said CONRED's Cabanas.
Mario Cruz, a spokesman for the volunteer firefighter corps, said 3,100 people had evacuated the area so far. Some ash also has fallen on the capital.
A volcano southwest of Guatemala's capital has erupted for the second time this year, setting off loud explosions and spewing ash almost four miles into the sky.
Ash has effected not only Guatemala City but the departments of Sacatepequez, Chimaltenango, Escuintla, and the popular tourist destination colonial town Antigua.
Volcan del Fuego is one of the most active volcanoes in Central America.
Lesser amounts of ash reached the capital of Guatemala City some 25 miles away, forcing the closure of its worldwide airport, CONRED said. Local media reported that the ash blanketed cars and houses in villages nearby.