A major 7.4 magnitude earthquake with an epicenter on Mexico's Pacific Coast shook central southern Mexico on Tuesday, causing buildings to sway and sending frightened workers and residents to scamper onto the streets as far as Mexico City.

Mexico's National Seismological Survey said the epicenter of the quake was 15 miles east of Ometepec, Guerrero and 10.9 miles underground. 

The initial quake near the borders of Oaxaca and Guerrero states was followed by a less powerful, magnitude-5.1 aftershock that also was felt in the capital.

Frightened workers and residents poured into the streets of the capital just minutes after noon local time. Telephone service was down in the city and throughout the area where the quake was felt.

About 40 passengers were stranded for a short time on the Mexico City airport air train, but later released. The airport closed for a time but officials said there was no runway damage and they resumed operations.

A pedestrian bridge collapsed and crushed a microbus in Mexico City, but there were still no reports of deaths. 

Mexico City Mayor Marcelo Ebrard sent a tweet saying 'we have an earthquake' in Spanish. Ebrard tweeted that he boarded a helicopter and saw no visible damage from the air.

He also said the water system and other "strategic services" were not experiencing problems and that Mexico City's Benito Juárez International Airport is functioning normally.

Mexican President Felipe Calderón also tweeted that there are no initial reports of major damage. 

As the epicenter was inland, there were tsunami watches issues for local waves and the Pacific tsunami alert was not issued. 

Lauren Villagran, a freelance reporter for Fox News Latino, who was walking in the streets of central Mexico City during the quake, told Fox News Latino that there doesn't seem to be major damage. 

Villagran was located in the central residential Condesa neighborhood, popular for its bars and restaurants. Residents, diners and kitchen staff gathered in the streets and watched a tall building anchored by nightclubs sway dangerously. A building in the neighborhood of Condesa appeared to be on the verge of collapsing, The Associated Press reported.

"Buildings shook, some windows have broken, the facades of some buildings have crumbled, some transformers busted," Villagran said. "The ground started to move, then rocked violently. As many as six aftershocks were felt around the city."

She added that a city official reported on the radio that a pedestrian bridge crumbled; there were reports of buildings leaning but no other major damage reported so far.

State television and politicians have reported no deaths.

Groups of women hugged and cried at Mexico City's Angel of Independence monument, where hundreds of people evacuated from office buildings said they never had felt such a strong earthquake. Others typed ferociously on their Blackberries, reported The Associated Press.

Samantha Rodriguez, a 37-year old environmental consultant, was evacuated from the 11th floor on the Angel Tower office building.

"I thought it was going to pass rapidly but the walls began to thunder and we decided to get out," she told AP.

Mexico City's airport was closed for a short time but there was no damage to runways and operations were returning to normal.

The White House said that President Barack Obama's oldest daughter, Malia, is safe and never was in danger during the earthquake in Mexico.

Malia, 13, is on vacation with a school group in Oaxaca, according to reports from the region. 

Kristina Schake, the first lady's communications director, said Malia Obama "is safe and was never in danger." Typically the White House does not comment on the Obama children but made an exception because of the quake.

Contains some reporting by the Associated Press.

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