At least 69 people, including children, are known to have died after rivers of lava made their way through remote mountain hamlets – but only 17 have been identified so far.
An official from the National Institute of Forensic Sciences said: “It is very difficult for us to identify them because some of the dead lost their features or their fingerprints.
“We are going to have to resort to other methods… and if possible take DNA samples to identify them.”
Emergency workers have faced challenging conditions as they dig through debris and mud in search of survivors – with smouldering terrain still hot enough to melt shoe soles.
Residents had little or no time to flee to safety – and now, rescuers are using sledgehammers to break through the roofs of houses buried in debris to see if anyone is trapped inside.
There have been reports of miracle survivors being wrenched to safety, with emergency crews in helicopters managing to pull at least 10 people out of areas cut off by the lava flows.
An estimated 3,271 others have been evacuated.
Coffins of some of the dead have been carried down crowded streets as residents begin to try to come to terms with the disaster that has befallen their communities.
President Jimmy Morales has travelled to survey affected areas.
Volcanologist Dr Rebecca Williams has warned that the emissions from the Volcano of Fire are “the most deadly event to happen at a volcano”.
Writing on Twitter, she explains that pyroclastic density currents are magma hot flows of rock, ash and gas.
The head of geology at the University of Hull says these currents “typically travel at speeds faster than a car can drive” with an estimated top speed of up to 450mph.
The fast-moving lava overtook people in homes and streets with temperatures reaching as high as 700C (1,300F), and hot ash and volcanic gases that can cause rapid asphyxiation.
Footage of huge, dark, swirling clouds from the area have circulated online and been broadcast on TV screens across the world.
Ms Williams explained: “The clouds you see mask a dangerous interior to these currents. Often a dense avalanche is at the base, capable of carrying huge blocks of rock. This has great force and will destroy buildings and flatten forests.”
The volcano, situated 25 miles (40km) southwest of the capital Guatemala City, has registered a number of minor eruptions over the years.
Some residents in El Rodeo, one of the worst-affected villages, have criticised Conred, Guatemala’s disaster agency, for not evacuating communities quickly enough.
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One of them, Rafael Letran, said: “When the lava was already here they passed by in their pickup trucks yelling at us to leave, but the cars did not stop to pick up the people.
“The government is good at stealing, but when it comes to helping people they lack spark.”