Rescue workers said Wednesday they believed they'd made contact with a girl trapped in the rubble at the school, where at least 19 children and six adults were killed.
For more than a day, rescuers told reporters they were trying to reach and free the girl -- efforts that were shown live on television.
But by Thursday afternoon, navy official Angel Enrique Sarmiento said all the school's children had been accounted for -- either having died, been hospitalized or found safe -- and there was no student known to be in the rubble.
Sarmiento, deputy navy secretary, followed up with an apology Thursday night, while emphasizing that someone still could be alive in the debris.
"I want to make it very clear that the information the Mexican public received about the existence of a girl who was alive underneath the rubble was released by the navy based on the technical reports and the accounts of the civilian and navy rescuers," he said.
"I offer the Mexican public an apology for the information disseminated (Thursday) afternoon where I affirmed that I did not have details about a supposed child survivor in this tragedy."
A search of the school continues, though the last time a body was found -- that of a 58-year-old woman, the navy said -- was Thursday morning.
Sarmiento did not provide details about why officials are leaving open the possibility of finding someone else alive in the collapsed school. Eleven people who either escaped or were helped out of the school already had been taken to a hospital.
Reports about the girl first came Wednesday when rescuers said they had come into contact with a trapped girl, and that temperature readings suggested others might be alive inside. Citing rescuers, CNN affiliate Foro TV initially reported that rescue teams had given the girl oxygen and water.
But seemingly contradictory information followed. By Thursday morning, navy Adm. Jose Luis Vergara had said that the girl's exact location wasn't known. And by the afternoon, Sarmiento's announcement all but ended the speculation about a trapped girl.
Details about what the rescuers may have encountered weren't immediately available.
Meanwhile, searches at other collapsed buildings in central Mexico continued Friday as volunteer brigades joined government efforts to reach possible survivors and clear away rubble. Amid the chaos, some Mexicans took comfort in how the disaster had brought them together.
Two earthquakes in 12 days
Tuesday's earthquake turned dozens of buildings in central Mexico into dust and debris, killing at least 286 people, including one in Oaxaca, almost 480 kilometers (300 miles) from Mexico City.
The temblor was the second major one to hit the country in less than two weeks
, following an 8.1 magnitude earthquake
farther south on September 8, killing nearly 100 people. Tuesday's quake hit hours after a citywide drill on the anniversary of the 1985 earthquake that killed an estimated 9,500 people
in and around Mexico City.
President Enrique Peña Nieto declared a national emergency, and the country is observing three days of national mourning. An unaccounted number of people are staying at shelters around Mexico City after losing their homes. Schools have closed indefinitely, and millions remain without power.
Despite Peña Nieto's request that people stay indoors while rescue attempts continue, residents joined forces with rescue teams to search for survivors.
'We know he is in there'
Throughout the region, buses carried volunteers from Mexico and beyond to disaster sites, where they bolstered search-and-rescue efforts. People formed human chains to pass along supplies and remove chunks of lumber and concrete.
It reminded some of the last time an earthquake of this scale hit the nation's capital. One man, who gave his name as Roberto, recalled pulling people out of wreckage in Mexico City 32 years ago. It was worse then, he said, crediting enhanced building regulations with minimizing the damage.
"I can remember the feeling of lifelessness in their bodies," he said. "I remember my hands sinking into their skin. They were decomposing. It was horrible."
In Mexico City's Condesa section, a large rescue operation was underway at a collapsed building that had housed an outsourcing company. At least 35 people are believed to still be buried in the rubble of the building on Alvaro Obregon.
Marco Antonio Garcia Salsedo said he believes his cousin is still alive in the building. His family heard that Angel Xavier Sousado Sandovar somehow placed a phone call to a friend in New York from inside the rubble.
The family has been camping out near the rescue site since Tuesday, holding out hope that Sousado would emerge from the building. The relatives don't want to miss an announcement, and they don't want the government to raze the site before their loved one is found.
"We know he is in there, and we are waiting for him," Garcia said.
Elsewhere in the neighborhood, police blocked a road leading to the corporate offices of a food processing center that also was damaged. Cristobal Perres Garcia, 59, said police told him that one of his cousins -- a worker at the building -- was among several who died when it collapsed.
In Puebla state, southeast of Mexico City, the quake crumbled a church, killing a girl who was being baptized
and 11 others attending the event, Gov. Tony Gali said. More than 9,700 homes and 100-plus government buildings were damaged in the state, Gali said.
In all, 148 deaths were reported in Mexico City, one of North America's most populous metropolises with more than 21 million people. Elsewhere, 73 deaths were reported in Morelos state, 45 in Puebla state, 13 in the state of Mexico, six in Guerrero state and one in Oaxaca state.
'I thought someone was kicking my chair'
About 2,000 public schools were damaged in Tuesday's quake, Secretary of Public Education Aurelio Nuños said. Sixteen of the 212 affected schools in Mexico City had serious damage, he said.
At the private Colegio Enrique Rabsamen, where rescuers thought they were trying to reach the girl, the temblor caused the school to fold in on itself, sandwiching and collapsing classroom onto classroom.
Crews remained there Thursday evening, but the sense of urgency had dissipated, along with the crowds of onlookers. In their place, well-wishers left bunches of white floral arrangements around the block from the school.
The loss of life weighed heavily on volunteers.
"This is a tragedy," said volunteer Ivan Ramos. "It's kids. It will take a long time to heal."