New evacuations have been ordered in Guatemala after searing hot ash and mud began flowing down the Volcano of Fire.
Rescuers and police have been pulled back from towns destroyed during the eruption on Sunday that killed at least 70 people.
Witnesses reported seeing a new column of smoke rising into the sky as a siren wailed and loudspeakers blared: "Evacuate."
Guatemala's seismology institute said the new flow of volcanic material down the southeastern slopes is expected to produce a "curtain" of ash.
The ash could reach heights of about 20,000ft above sea level and is expected to be carried by the wind to the west and north-west.
Civil aviation authorities are being ordered to take precautions with air traffic.
At 1pm local time the disaster agency, known as Conred, confirmed the death toll stood at 70 - but this figure is expected to rise as rescue work continues.
It said a total of 1.7 million people have been affected by the eruption, with 3,271 evacuated, and 2,625 being housed in shelters.
Conred spokesman Juan Sanchez said that there was little chance of finding anyone alive 72 hours after the eruption.
"The condition in which the homes are makes that possibility pretty unlikely," he said.
In the devastated town of El Rodeo, rescuers wearing hard hats, masks and goggles had been using shovels to dig through homes.
Only 17 of the bodies recovered so far have been identified due to the extreme heat that burned them beyond recognition.
Many dogs and cats were rescued with burns on their paws from the mud and ash and some were blinded from the volcanic gases.
AP contributed to this report.