Workers repair subway lines in Mexico City that were damaged by a magnitude… (Associated Press )
Reporting from Mexico City — A powerful and prolonged earthquake rocked Mexico on Tuesday, toppling houses near the epicenter in the south, cracking building facades in this sprawling capital and briefly terrifying a population well schooled in natural disasters.
Despite the quake's 7.4 magnitude, however, there were no reports of serious injury, according to President Felipe Calderon and officials across the country. Aftershocks rattled the area through the rest of the day.
"This is one of the strongest we've ever felt," said Calderon, who urged Mexicans to remain calm.
PHOTOS: Earthquake hits Mexico
In this capital of 20 million, the quake shook office buildings and apartment houses and sent hundreds of thousands of people into the streets. A pedestrian bridge on the outskirts of the city was wrenched from its girders and crushed a passenger bus below. The bus was empty save for the driver, who escaped with minor injuries.
The brunt of the shaking apparently was taken by the southern states of Guerrero and Oaxaca, near whose shared border the epicenter of the quake was pinpointed 12 miles below the surface. Guerrero Gov. Angel Aguirre said more than 500 small homes in two remote villages were damaged, with at least 60 of them collapsed.
Oaxaca Gov. Gabino Cue reported cracks and broken windows in several schools and minor damage to a number of Oaxaca City's iconic monuments and colonial-era buildings. He said signposts had fallen in the city, and the quake had triggered small landslides on a handful of rural roads.
The third floor of a university being remodeled collapsed, he added. Five people were injured in those incidents, none of them seriously, authorities said.
President Obama's older daughter, Malia, was vacationing in Oaxaca with school friends but was not hurt, White House officials said. Malia, 13, "is safe and was never in danger," said First Lady Michelle Obama's spokeswoman, Kristina Schake.
In Mexico City, the shaking revived memories of the devastating 1985 quake that destroyed parts of the capital and killed more than 10,000 people. Because of that and other natural disasters, residents here periodically rehearse evacuations and other emergency procedures.
That practice was on full view Tuesday. Although there were, as Calderon put it, scattered "scenes of panic," many of the evacuations were orderly. Workers, from executives in business suits to the aproned cleaning staff, filed from offices, down stairs and into the streets, where they gathered at predesignated spots. Pre-assigned marshals donned rescue vests and made sure everyone was accounted for. Evacuation alarms screeched in the background.
Hours later, many had not returned to their buildings. Officials from the federal attorney general's office were working in a nearby Starbucks.
Mexico City Mayor Marcelo Ebrard, who within minutes of the temblor took to the skies in a helicopter to survey the city, said the toll seemed limited to cracked walls, loosened plaster and tilting buildings. Telephone service and electricity to more than 2 million customers were interrupted for several hours, traffic lights went blank, and one hospital said it would close and transfer patients to another facility because of damage.
The federal Chamber of Deputies, the lower house of Congress, was in the middle of a legislative debate when members were told to clear the building. An enormous crystal chandelier swayed precariously back and forth above the chamber, casting an odd light over the scurrying legislators.
When the quake hit at 12:02 p.m., there was an initial rocking, a pause and then a much stronger, sustained bouncing motion.
The U.S. Geological Survey initially measured the quake at magnitude 7.6, then revised its reading to 7.4. The epicenter was in Guerrero state about 115 miles east of the tourist resort of Acapulco and 100 miles west of Oaxaca City.
PHOTOS: Earthquake hits Mexico