Guatemalan rescuers searched Thursday for people trapped in the ruins of homes after a powerful earthquake killed 52 people and left thousands spending the cold night outside.

Twenty-two people were still missing a day after the 7.4-magnitude quake in the southwestern region of San Marcos toppled homes and cut off power in several towns.

The search had been called off during the night for safety reasons.

Thousands of people in the town of San Marcos wrapped themselves in blankets to keep warm outside overnight as aftershocks continued to rock the mountainous region.

Rescuers found three more bodies in the town of San Cristobal Cucho on Thursday and another one in El Recreo, a firefighters' spokesman said.

President Otto Perez said Thursday the death toll had risen to 52 from 48 the day before. Power was restored in 95 percent of homes, he added.

The San Marcos department, located at the border with Mexico and some 250 kilometers (155 miles) west of Guatemala City, bore the brunt of the earthquake, which crushed cars and spread debris on roads.

In San Cristobal Cucho, an entire family of 10, including six children, died when their home was buried in rocks and earth that slid from a hill after the earthquake, Mayor Pedro Cardona said.

"The whole village is in mourning because an entire family was taken by God's nature," he told local television. "What can we do?"

Some 16,000 people were affected by the temblor, which was the country's most violent seismic event since 1976, when almost 23,000 people perished.

Authorities opened 11 shelters that can house 800 people.

The United States offered help to victims Thursday, announcing it was providing some $50,000 in immediate aid and had helicopters on standby to ferry supplies.

"Our heartfelt condolences go out to the people of Guatemala for the tragic loss of life and property resulting from yesterday's earthquake," State Department spokeswoman Victoria Nuland said.

The earthquake was felt as far away as El Salvador and Mexico City. Thousands of people fled homes, offices and schools in the Mexican capital when the quake hit on Wednesday morning.

The US Geological Survey said the quake struck Wednesday morning off the Pacific coast, some 24 kilometers south of Champerico and 163 kilometers west-southwest of Guatemala City. The depth was 41.6 kilometers.

The streets of San Marcos, a town dotted with colonial-style, single-floor homes, were covered in debris. Older homes were in pieces but newer ones withstood the shock.

Several aftershocks rattled residents, who used lamps to look for pillows and covers in what was left of their homes to keep warm during the night.

On Wednesday, rescue workers and residents looked for people buried in sand in a quarry.

"We feel powerless in front of this quantity of sand, which fell on people, and not being able to dig them out quickly," 30-year-old social worker Alfonso told AFP. "You feel like your hands won't reach people."