SAN MIGUEL LOS LOTES, Guatemala — Emergency crews cautiously resumed search-and-rescue operations Wednesday in towns and villages devastated by the eruption of Guatemala’s Volcano of Fire, but time was quickly running out to find survivors of a disaster that killed more than 75 people with another nearly 200 still missing.

Thousands of people displaced by the eruption have sought refuge in shelters, many of them with dead or missing loved ones and facing an uncertain future, unable to return to homes destroyed by the volcano.

Firefighters said the chance of finding anyone alive amid the still-steaming terrain was practically nonexistent 72 hours after the volcanic explosion on Sunday. The thick gray ash covering the stricken region was hardened by rainfall, making it even more difficult to dig through the mud, rocks and debris that reached to the rooftops of homes.

“Nobody is going to be able to get them out or say how many are buried here,” said Efrain Suarez, standing amid the smoking holes dotting what used to be the village of San Miguel Los Lotes on the flanks of the mountain.

“The bodies are already charred,” the 59-year-old truck driver said. “And if heavy machinery comes in they will be torn apart.”

Once a verdant collection of canyons, hillsides and farms, the terrain is now a barren moonscape. Rescuers poked metal rods into the ground, sending clouds of smoke pouring into the air in a sign of the super-hot temperatures still remaining below the surface, which firefighters said reached as high as 750 to 1,300 degrees Fahrenheit in some places.

At a shelter in the Murray D. Lincoln school in the city of Escuintla, about 10 miles from the volcano’s peak, Alfonso Castillo said he and his extended family of 30 had lived on a shared plot in Los Lotes where each family had its own home.

Everyone was accustomed to the volcano, one of Central America’s most active, rumbling and spewing smoke, the 33-year-old farm worker said, so at first nothing seemed abnormal on Sunday. But then a huge cloud of ash came pouring out.

“In a matter of three or four minutes the village disappeared,” Castillo said.

His family was rescued, but the life they knew was gone.