Workers poked metal rods into the terrain to release smoke, an indication that super-hot temperatures remained below the surface three days after the volcanic explosion that killed at least 75 people.
"You can't say all pyroclastic flows are always more risky than all lava flows, but you can generally say that pyroclastic flows are more unsafe than lavas overall", said Ken Rubin, chair of the Department of Geology and Geophysics and the University of Hawaii.
A rescue worker pauses amid the attempt to save people hurt or displaced in the eruption.
Homes and structures in villages at the foot of the volcano, including hard-hit El Rodeo, were covered in ash and mud, leaving the once lush, green vegetation coated in gray.
Nigeria has condoled with the Government and People of the Republic of Guatemala over the Fuego volcano tragedy in the country.
"If you are trapped in a pyroclastic flow, it's hard to come out of it alive", he said, adding that if people caught in the flow they may never be found.
A thick layer of still smoldering ash and volcanic rock blanketed the tiny hamlet of San Miguel Los Lotes, with only the roofs of some homes sticking out.
Hernandez and her husband, Francisco Ortiz, survived because they moved out of Los Lotes just two months ago to begin a new life on a small plot of land.
Kilauea Lava Flow Rolls Into Sea at Kapoho Bay
There have been various arrests of people forcing their way through blocked areas. "This could go on for months", she said. Tuesday, the volcano began spewing ash almost a mile into the air, sparking a 5.5 magnitude quake , according to the U.S.
Figures for the dead were tweeted by Guatemala's National Institute of Forensic Sciences.
The Fuego volcano erupted yesterday, sending lahars down the side of the mountain and huge plumes of ash into the air.
The institute says only 23 of the recovered bodies have been identified so far.
"We will continue until we find the last victim, though we do not know how many there are".
The U.S. military was expected to fly children burned by hot ash and volcanic debris to the Galveston Shriners Hospital pediatric burn center in Galveston, Texas. Numerous victims are unrecognisable, with officials warning that DNA testing and other methods may be needed to identify them.
Authorities say at least 46 people were injured in the eruption, and 12 shelters were housing 1,877 people.
A rescue team from Israel is also aiding with rescue efforts.
As dawn broke today, the volcano continued to rattle with what Guatemala's Volcanology Institute said were eight to 10 moderate eruptions per hour - vastly less intense than Monday's big blasts.