SAN VICENTE, El Salvador, Feb. 14 (AP) -- This small Salvadoran city was lucky last month. A 7.6-magnitude earthquake that completely buried a neighborhood under a massive landslide left its clusters of humble adobe homes untouched. But San Vicente's luck turned deadly Tuesday, when a powerful 6.6-magnitude earthquake flattened hundreds of homes, burying 13 people and injuring more than 500, including children and the elderly.

"My house just came tumbling down," said 80-year-old Maria Aguilar, her eyes filled with tears at the town's central hospital. "Part of a wall collapsed on top of me, but my grandchildren rescued me quickly."

The death toll from Tuesday's quake reached 255 on Wednesday, mostly from collapsed homes, said the National Emergency Committee. At least 2,261 were reported injured.

Among the victims were six kindergarten students and their 25-year-old teacher, killed when their parochial school collapsed in the small town of Candelaria, 25 miles east of the capital, San Salvador. The teacher, Anabel Chavez, was found with her arms wrapped around some of the children.

"The church and the school are literally flat on the ground," said Oswald Guerra, deputy commissioner of the national civil police.

All of the schoolchildren were between the ages of 4 and 6, Guerra said. He said another 40 children received leg and arm injuries.

President Francisco Flores took a helicopter tour to assess the damage to the country of 6 million people.

"It is true that this is another blow for El Salvador, but I call for tranquility. We have to be calm," he told The Associated Press.

Flores later noted that the quake's impact on the affected towns "is greater than what happened on Jan. 13," the date of the 7.6-magnitude quake that officials say killed 844, injured 4,723 and destroyed 278,000 houses. Hundreds more remain missing and are believed dead.

Tuesday's quake compounded the misery of a nation struggling to cope. January's quake, centered off El Salvador's southern coast, triggered a landslide that buried hundreds of people in the city of Santa Tecla. The city was not affected by Tuesday's temblor.

The U.S. Geological Survey said the new quake was centered near the midpoint between San Vicente and San Salvador. The quake struck at 8:25 a.m. Hardest hit were the provinces of San Vicente, Cuscatlan and La Paz, in the center, where at least 167 people were killed, the emergency committee said. In Candelaria, at least 39 people were killed, 57 were injured and two were missing. A total of 1,300 houses were ruined and another 600 damaged.

"The community is practically destroyed," Guerra said.

Officials said the death toll could sharply increase due to numerous landslides that had blocked highways and prevented access to some communities. Flores said army brigades were working to rescue an unknown number of people buried in rural landslides.

Flores said the Panamerican Highway was heavily damaged and would be out of service for the foreseeable future.

He also said that San Salvador, which was not affected seriously by the quake, had no drinking water after pipes in the city collapsed. The quake was felt strongly because it was shallow, centered below land rather than the sea.

San Vicente, a city of more than 40,000 and capital of the province of the same name about 40 miles east of San Salvador, was almost flattened.

"This was horrible,'' said Maria Lozano, 44, whose 86-year-old father, Clemente Lozano, was killed when a wall in their home fell on him. Lozano waited anxiously for her father's body to arrive at a hospital. Her mother was still missing.

Regional army commander Col. Juan Armando Reyes said half of the houses were damaged in San Vicente, a figure that rose to 90 percent in the nearby towns of San Cayetano, Guadalupe, Verapaz and Texistepeque.

Streets in San Vicente were buried under mountains of debris. Frightened families erected tents outside the ruins of their collapsed adobe houses, and flocked to parks and sports stadiums that had been converted into temporary refuges.

A small aftershock struck as Flores toured a hospital in San Vicente, where hundreds of patients were sprawled on the floor or the grounds outside for lack of beds.

The government sent students home across the country and evacuated most public buildings, including many hospitals, so they could be checked for possible damage. San Salvador's airport also was briefly closed.

Emergency officials said at least three people died when a grain silo collapsed in San Martin, about 10 miles east of the capital.

When the quake struck, hundreds of thousands of people fled into the streets of the capital -- a city jittery from more than 3,200 aftershocks of the Jan. 13 quake, several surpassing magnitude 5.

Even Flores was displaced by the January quake. With his office damaged, he has been working out of temporary quarters at a fairgrounds.