President Otto Perez Molina said the powerful 7.4-magnitude quake that hit Wednesday morning off the Pacific coast affected as many as 1.2 million people. He said a little more than 700 people were in shelters, with most opting to stay with family or friends.
"They have no drinking water, no electricity, no communication and are in danger of experiencing more aftershocks," Perez told a news conference. The president said there had been 70 aftershocks in the first 24 hours after the quake, some as strong as magnitude 4.9.
Damaged homes will be among the biggest problems the country will face in the coming days, Perez added.
Guatemalans fearing aftershocks huddled in the streets of the mountain town of San Marcos, the most affected area, where at least 40 people died. Others crowded inside its hospital, the only building left with electricity.
More than 90 rescue workers continued to dig with backhoes at a half-ton mound of sand at a quarry trying to rescue seven people.
"We started rescue work very early," said Julio Cesar Fuentes of the municipal fire department. "The objective is our hope to find people who were buried."
But they uncovered only one more body, that of one of the quarry workers. The worker's son was called to identify him. When he climbed into the sand pit and recognized the clothing, the man collapsed onto the shoulders of firefighters, crying: "Papa, Papa, Papa."
He and his father were not identified to the news media because other relatives had not been notified of the death.
Residents venturing outside into the morning cold found the city paralyzed and businesses closed.
In the town of San Cristobal Cochu, firefighters picked at a collapsed house trying to dig out 10 members of one family, including a 4-year-old child, who were buried, fire department spokesman Ovidio Perez told the radio station Emisoras Unidas.
Volunteers carrying boxes of medical supplies began arriving in the area in western Guatemala late Wednesday.
Eblin Cifuentes, a 26-year-old law student, and a group of his classmates already were collecting medical supplies as part of a school drive to provide aid for the only hospital in San Marcos, a poor, mainly indigenous mountain area of subsistence farms. When the quake hit, the group decided to bring everything they had collected.
"Thank God nothing happened to us and that's why we have to help out," Cifuentes said.
The quake caused terror over an unusually wide area, with damage reported in all but one of Guatemala's 22 states and shaking felt as far away as Mexico City, 600 miles (965 kilometers) to the northwest.
In San Marcos, more than 30 homes were damaged and many of the colorful adobe buildings in its center were either cracked or reduced to rubble, including the police station and the courthouse. The temblor tore a large gash in one of the streets. Hundreds of frightened townspeople stayed in the open, refusing to go back inside after more than five strong aftershocks shook the area.
Eight were killed in the neighboring state of Quetzaltenango.
Hundreds of people crammed into the hallways of San Marcos' small hospital after the quake seeking help for injured family members. Some complained they were not getting care quickly enough.
Ingrid Lopez, who bought in a 72-year-old aunt whose legs were crushed by a falling wall, said she had waited hours for an X-ray.
"We ask the president to improve conditions at the hospital," she said. "There isn't enough staff."
Efrain Ramos helped load a tiny casket carrying the body of his 6-year-old niece from the San Marcos morgue to a waiting pickup truck.
"The little girl died when a wall fell over her," a shocked Ramos told a reporter. He said the girl was playing in her room when the quake hit.
Sobbing uncontrollably, the girl's mother hugged the coffin wrapped with white lace and tulle.
Ramos said the family would escort his niece Rosa's body back home for a viewing.
The quake, which was 20 miles deep, was centered 15 miles off the coastal town of Champerico and 100 miles southwest of Guatemala City. It was the strongest earthquake to hit Guatemala since a 1976 temblor that killed 23,000.
Perez said more than 2,000 soldiers were deployed to help with the disaster. A plane had made at least two trips to carry relief teams to the area.
Associated Press writer Sonia Perez-Diaz and Michael Weissenstein reported this story in San Marcos and Romina Ruiz-Goiriena reported from Guatemala City.