National disaster agency Conred said 192 people remained missing and the forensic agency, Inacif, raised the death toll to at least 75, up from 72.
Guatemala's authorities warned that the Fuego volcano was showing signs of greater activity on Tuesday night as the death toll from a devastating eruption at the weekend climbed to 75 and nearly 200 people remained missing.
The seismological, volcanic and meteorological institute Insivumeh heightened its warnings after the volcano erupted again earlier on Tuesday, forcing evacuations and sending rescue workers scrambling for cover.
The national disaster agency, Conred, said 192 people remained missing after the disaster and the forensic agency, Inacif, raised the death toll to at least 75, up from 72.
As of 13:00 local time Tuesday, more than 1,700,000 people had been affected, with 3,271 forced to evacuate.
The peak had its most devastating eruption in more than four decades on Sunday, showering ash on a wide area and sending lava flows through nearby towns, according to a Reuters report.
"The conditions are extremely critical at this moment," Insivumeh Director Eddy Sanchez told reporters.
Volcan de Fuego, which means 'Volcano of Fire' in Spanish, is one of several active volcanoes among 34 in the Central American country. It lies near the colonial city of Antigua, a Unesco world heritage site that has survived several major eruptions.
The latest activity has been mostly on the far side of the volcano, facing the Pacific coast.
The eruption on Sunday sent columns of ash and smoke 6.2 miles into the sky, dusting several regions with ash. Thousands of people have been evacuated, Conred said.