MEXICO CITY -- A strong earthquake rocked Mexico Wednesday, measuring a magnitude 7.0.
The USGS says the quake was centered in a sparsely populated mountainous area in Mexico's Michoacan state about 209 miles west-northwest of Acapulco.
Two weeks ago, a magnitude 7.4 quake hit the country east of Ometepec, Guerrero causing widespread damage.
At least 500 homes in the southern coastal state were damaged, Gov. Angel Aguirre told reporters.
Nine of the 11 injuries occurred in Oaxaca state, which borders Guerrero and also suffered damage from the quake, said Mexican Interior Minister Alejandro Poire.
Authorities said two people were injured in Mexico City, including the driver of a minibus that was crushed when a pedestrian bridge collapsed during the quake.
Guerrero residents felt aftershocks hours after the initial earthquake, which the U.S. Geological Survey said had a depth of about 12.4 miles (20 km).
Many residents, fearing aftershocks, said they slept outdoors overnight.
Residents rushed into the streets after feeling the temblor in Mexico City. Tourists and residents also felt the earthquake in the resort city of Acapulco, located about 100 miles (200 km) from the quake's epicenter.
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.
The USGS initially reported the magnitude of the quake at 7.9, but later revised that figure downward to 7.4.
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, Aguirre told CNN affiliate Televisa.
Authorities in Mexico City were surveying buildings, schools and hospitals to evaluate damage, Mayor Marcelo Ebrard said.
Earthquakes are a frightening experience for the more than 20 million residents who live in the sprawling metropolis, where about 10,000 people perished 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.