The Fuego volcano, located about 50 kilometers (31 miles) south of this capital, on Sunday spewed a column of ash up to a kilometer (about 3,300 feet) high, a government agency reported.
The National Vulcanology Institute said in a communique that the volcano, which rises 3,763 meters (12,230 feet) above sea level, on Sunday erupted effusively, according to seismic recordings and the images received from a camera at the observatory at Panimache.
The volcano's activity presently consists of emissions of red hot lava being hurled from the crater to a height of some 500 meters (1,625 feet), the agency said.
The institute went on to say that three rivers of lava were emerging from the crater and moving down the sides of the mountain.
In addition, two emissions of ash rising from 800 to 1,000 meters (about 2,600 feet to 3,300 feet) were blowing southeast.
The vulcanology institute warned that although the eruption presently consists of an effusion of lava, the possibility exists that in the coming hours the volcano's activity will increase to a pyroclastic flow of the kind experienced on May 19 and May 25.
A pyroclastic flow is a fast-moving current of superheated gas, which can reach temperatures of about 1,000 C (1,830 F), and rock, which reaches speeds moving away from a volcano of up to 700 km/h (450 mph). The flow normally hugs the ground and travels downhill, or spreads laterally under gravity, and is quite devastating to virtually anything in its path.
The agency recommended to the Conred disaster organization to maintain an orange preventive alert near the mountain until the volcanic activity lessens.
Civilian air traffic is being warned to take precautions because the ash cloud extends up to 10 kilometers (6.2 miles) from the volcano.
The Fuego volcano, whose name in the Kakchikel Indian language is "Chi Cag" (where the fire is), is one of the most impressive fire mountains in Central America and has been in a constant state of activity.
So far, civil protection authorities do not think that the eruption represents a danger for nearby towns, but it is recommending that residents in the region be on alert to take whatever measures Conred may announce. EFE