A new quake sowed panic in Mexico City on Saturday, causing no casualties but suspending rescue operations to free survivors from the earlier, more powerful earthquake this week that devastated parts of the capital.
The seismic disturbance, with a magnitude of 6.2, was smaller and farther to the south than the 7.1-magnitude one that struck on Tuesday, killing nearly 300 people and toppling 39 buildings in the capital.
But as an alarm sounded, residents raced out into the street, some barefoot, some carrying children. Trauma from the previous quake was evident.
"Oh God, have mercy," exclaimed Teresa Martinez, 74, who had run out in to the street for safety. She and other woman stood around in tears.
"This time we didn't feel the ground move... maybe since the last one we're getting used to them," said Pablo Martinez, who had run out of his central apartment block with his 6-year-old daughter in his arms.
The new tremor sparked concern it could have caused heavy rubble on top of survivors awaiting rescue in the capital to shift -- posing a danger both to those trapped and to rescuers.
Mexican and foreign rescue crews rapidly evacuated three sites in the capital where they had been working.
At one site, where possibly dozens of people were under the debris, crews hesitated to go back in, discussing the added risk.
The US Geological Survey initially registered it at 6.2 magnitude, but later lowered it to a 6.1. The quake occurring at 12:53 GMT with an epicenter 18 kilometers (11.6 miles) southeast of the city of Matias Romero, in the southern state of Oaxaca.
The head of Mexico's civil protection service, Luis Felipe Puente, tweeted that there were no casualties immediately reported, adding: "We are continuing to monitor."
A bridge near the town of Juchitan collapsed, however, with television images showing it severed and buckled.
In Mexico City, anxious families have been carrying out vigils at the flattened sites where their relatives were when Tuesday's quake hit.
They have been urging exhausted emergency workers to keep trying to reach them, despite the 72-hour window for likely survival to have closed.
"A lot of time has passed (since Tuesday's quake). But we won't give up," the civil protection service's Puente said.
"Time has gotten the best of us. There are structures that are very complicated to access. But we're going to keep fighting for the families," he told TV network Televisa.
But psychologists dispatched to the scene were already preparing to help relatives deal with tragic news.
"The families are still hopeful, but we psychologists are starting to prepare ourselves to counsel them in the context of mourning," said Penelope Exzacarias, who was on standby at a collapsed office building in Mexico City's trendy Roma neighborhood.
Some 70 people were at work in the building when the 7.1-magnitude earthquake struck. Only 28 have made it out alive so far -- all in the first hours.
Many Mexicans remember "miracle" rescues a week after a 1985 quake that killed more than 10,000 people in the capital, spurring hopes that people might yet be pulled out alive.
In all likelihood, however, the death toll will rise above the latest figure of 295.
Mexico City recorded the highest number of fatalities: 157, with more bodies certain to be found.
The rest of the deaths occurred in the states of Morelos, Mexico, Puebla, Guerrero and Oaxaca.
The toll includes eight foreigners: four Taiwanese, a Korean, a Spaniard, a Panamanian and an Argentine, authorities said.
Several countries, including the United States, Israel, Japan, Panama and EU states have sent crews to help the rescue effort.
At the building in the Roma district, Jose Gutierrez, father of one of those trapped, and also a civil engineer, warned that "the structure is at risk of total collapse."
Saturday's new quake escalated those fears.
In the south of Mexico City, at a flattened school where 19 children died, white wreaths lay out, testimony to the mourning of relatives and neighbors.
Families were starting to hold funerals. One of the first was that of Gabriel Morales and Agueda Mendoza, a married couple found locked in embrace under the rubble along with their dog Quino.
"I remember them as such a united, loving couple," said Juan Carlos Williams, their nephew.