MEXICO CITY (CNN) -- Hundreds of houses collapsed after a strong earthquake that rattled residents in southern Mexican resort towns and the nation's capital Tuesday, officials said.
The quake had a magnitude of 7.4, according to the U.S. Geological Survey.
Its epicenter was about 15 miles (25 kilometers) east of Ometepec, Guerrero, the USGS said, and its depth was about 12.4 miles (20 km).
In the nearby town of Igualapa, officials reported that at least 800 houses had collapsed, the Guerrero state government said in a statement. There were no immediate reports of serious injuries or deaths.
More than an hour after the quake, residents in Ometepec were feeling aftershocks, said Francisca Villalva Davila, the city's comptroller.
"There are many cracked ceilings, many houses that collapsed," she told CNN en Español.
About five out of every 10 houses in the municipality, where about 50,000 people live, saw significant damage, the comptroller said.
"Tiles are falling. We are feeling constant aftershocks. It's shaking right now," she said.
The USGS initially reported the magnitude of the quake at 7.9, but later revised that figure downward. Mexican President Felipe Calderon said in a Twitter post it was 7.8.
Residents rushed into the streets after feeling the temblor in Mexico City, about 200 miles (320 km) away from the epicenter. Tourists and residents also felt the earthquake in the resort city of Acapulco.
Calderon said that there were no immediate reports of serious damage, and that the nation's health system was operating normally.
"There are some broken windows, much fear, much panic," he said.
Residents in the southwestern states of Oaxaca and Guerrero and the eastern state of Veracruz reported that phone service had been knocked out.
Multiple houses collapsed in the Ometepec area, but officials have no reports of deaths or injuries, Guerrero state Gov. Angel Aguirre told CNN affiliate Televisa.
Government helicopters were surveying the area, he said, and officials were preparing shelters for displaced residents, he said.
Authorities in Mexico City were surveying buildings, schools and hospitals to evaluate damage, Mayor Marcelo Ebrard said.
A pedestrian bridge fell on a minibus during the quake, he said, but there were no injuries.
Some buildings had cracks and broken windows, he said in a Twitter post.
Earthquakes are a frightening experience for the more than 20 million residents of Mexico City, where about 10,000 people perished in the area after a massive quake in 1985.
The city, built on volcanic ash and clay, is particularly vulnerable to temblors.
A spokeswoman told reporters that U.S. President Barack Obama's eldest daughter, who was on a spring trip with classmates in Mexico about 100 miles away from the quake's epicenter, was not injured.
"In light of today's earthquake, we can confirm that Malia Obama is safe and was never in danger," said Kristina Schake, a spokeswoman for first lady Michelle Obama.
CNN's Rey Rodriguez, Rene Hernandez, Ariel Crespo, Camilo Egana, Carloo Mauricio Perez, Esprit Smith, Rafael Romo, Nick Valencia, Phil Gast and Catherine E. Shoichet, journalist Salomon Kaufman and CNNMexico.com contributed to this report.