Almost 3,100 people have been evacuated from the affected area, the country's disaster management agency said.
CONRED said the number of dead had risen to 25, from an earlier estimate of seven, including a CONRED employee.
Dozens of people are missing with over 2,000 more having been evacuated from the affected areas, the Noticias 4Vision broadcaster reported.
It is the second major eruption this year from the peak, following another that subsided at the beginning of February after sending ash towering 1.7 kilometers into the sky.
Seven people have been killed and almost 300 injured after Guatemala's Fuego volcano erupted, officials say.
The National Disaster Management Agency (Conred) said a river of lava hit the village of El Rodeo, destroying houses and burning people inside. The victims included at least three children, two of whom burned to death while watching the eruption from a bridge.
Around 3,100 people have been evacuated from nearby communities into shelters.
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"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", Cabanas explained, speaking on local radio. "Evacuations and searches are under way", he said, quoted by Reuters.
It added that he said authorities began to send bulletins on the situation starting at 11:30 a.m.
The president said he and his government would determine whether to ask Congress to declare a state of emergency in the areas, while at the same time appealing to the population for calm.
"We have shut it down as a precautionary measure for the planes because the volcanic ash is harmful to the turbines", the airport spokesman, Francis Argueta said.
The volcano, whose name means fire, is one of Central America's most active.. The explosion rained soot over the popular tourist destination and other villages in the Sacatepéquez department, covering them in ash.
The Foreign Office advised Britons travelling to and from Guatemala to check with their airlines after La Aurora International Airport is expected to remain closed until at least 2pm (8pm BST) on Monday.