MEXICO CITY -- Rescuers found a surviving child on Wednesday in the ruins of a school that collapsed in Mexico's magnitude 7.1 earthquake, one of many efforts across the city to try to save people trapped in debris under schools, homes and businesses toppled by the quake that killed at least 223 people.

Authorities had earlier placed the death toll at 225 before reducing it Thursday afternoon.

Helmeted workers labored throughout the day, sometimes calling for silence to listen for any voices from the wreckage as they tried to reach the girl at the Enrique Rebsamen school in southern Mexico City. Journalists at the scene saw three rescuers entering the rubble.

Rescuers spotted the girl and shouted to her to move her hand if she could hear them, and she did, according to Foro TV. A search dog was then sent into the wreckage to confirm she was alive.

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Adding poignancy and a touch of the surreal, Tuesday's quake struck on the 32nd anniversary of the 1985 earthquake that killed thousands. Just hours earlier, people around Mexico had held earthquake drills to mark the date.

One of the most desperate rescue efforts was at the primary and secondary school, where a wing of the three-story building collapsed into a massive pancake of concrete slabs. Journalists saw rescuers pull at least two small bodies from the rubble, covered in sheets.

Volunteer rescue worker Dr. Pedro Serrano managed to crawl into the crevices of the tottering pile of rubble at the school. He made it into a classroom, but found everyone inside dead.

"We saw some chairs and wooden tables. The next thing we saw was a leg, and then we started to move rubble and we found a girl and two adults - a woman and a man," he said. All were dead.

"We can hear small noises, but we don't know if they're coming from ... the walls above, or someone below calling for help," he said.

CBS News correspondent Manuel Bojorquez reports that parents hung pieces of paper with the names of missing children, some of whom were subsequently found.

Names of children from #MexicoCity school that collapsed. Some are marked found, others still unaccounted for @CBSNews #MexicoEarthquake pic.twitter.com/8IrEKlIY73 — Manuel Bojorquez (@BojorquezCBS) September 20, 2017

Neighborhood volunteers, police and firefighters used trained dogs and their bare hands to search through the school's ruins. The crowd of anxious parents outside the gates shared reports that two families had received WhatsApp messages from girls trapped inside, but that could not be confirmed.

Rescuers brought in wooden beams to shore up the fallen concrete slabs so they wouldn't collapse further and crush whatever air spaces remained.

The federal Education Department reported late Tuesday that 25 bodies had been recovered from the school's wreckage, all but four of them children. It was not clear whether those deaths were included in the overall death toll of 223 reported by the federal civil defense agency. Mexican President Enrique Pena Nieto had earlier reported 22 bodies found at the school and said 30 children and eight adults were reported missing.

In a video message released late Tuesday, Pena Nieto urged people to be calm and said authorities were working to restore power and other services to the 40 percent of Mexico City and 60 percent of nearby Morelos state that lost electricity. But, he said, "the priority at this moment is to keep rescuing people who are still trapped and to give medical attention to the injured people."

"Every minute counts to save lives," the president tweeted.

The earthquake came less than two weeks after another powerful quake caused 90 deaths in the country's south.

People across central Mexico already had rallied to help their neighbors as dozens of buildings tumbled into mounds of broken concrete. Mexico City Mayor Miguel Angel Mancera said buildings fell at 44 sites in the capital alone as high-rises across the city swayed and twisted and hundreds of thousands of panicked people ran into the streets.

The huge volunteer effort included people from all walks of life in Mexico City, where social classes seldom mix. Doctors, dentists and lawyers stood alongside construction workers and street sweepers, handing buckets of debris or chunks of concrete hand-to-hand down the line.

Even Mexico City's normally raucous motorcycle clubs swung into action, using motorcades to open lanes for emergency vehicles on avenues crammed with cars largely immobilized by street closures and malfunctioning stoplights.

Economist Alfredo Coutino, Latin America director for Moody's Analytics warned Wednesday of economic disruption to several central states and the capital in particular.

"Though it is too early for authorities to have an estimate of the damage as rescue work continues, it is certain that economic activity ... will continue to be disrupted for some time," Coutino wrote.

The official Twitter feed of civil defense agency head Luis Felipe Puente said there were 94 dead in Mexico City and 71 in Morelos state, which is just south of the capital. It said 43 others were killed in Puebla state, where the quake was centered. Twelve deaths were listed in the State of Mexico, which borders Mexico City on three sides, four in Guerrero state and one in Oaxaca.

At the site of a collapsed apartment building in Mexico City, rescuers stood atop a three-story pile of rubble, forming a human chain that passed pieces of rubble across four city blocks to a site where they were dumped.

Throughout the day on Tuesday, rescuers pulled dust-covered people, some barely conscious, some seriously injured, from about three dozen collapsed buildings. At one site, shopping carts commandeered from a nearby supermarket were used to carry water to the rescue site and take rubble away.

Rescue workers look at fellow workers searching for people under rubble of collapsed building after earthquake hit Mexico City on September 19, 2017 CARLOS JASSO / REUTERS

As night fell, huge flood lights lit up the recovery sites, but workers and volunteers begged for headlamps.

Where a six-story office building collapsed in Mexico City, sisters Cristina and Victoria Lopez Torres formed part of a human chain passing bottled water.

"I think it's human nature that drives everyone to come and help others," Cristina Lopez said.

"We are young. We didn't live through '85. But we know that it's important to come out into the streets to help," said her sister, Victoria.

Ricardo Ibarra, 48, did live through the 1985 quake and said there hadn't been anything like it since.

Wearing a bright orange vest and carrying a backpack with a sleeping bag strapped to it, he said he and his friends just wanted to help.

"People are very sensitive because today was the 32nd anniversary of a tragedy," he said.

Nurses stand next to cribs with small children after they were evacuated after earthquake hit Mexico City on September 19, 2017 CARLOS JASSO / REUTERS

Buildings also collapsed in Morelos state, including the town hall and local church in Jojutla near the quake's epicenter. A dozen people died in Jojutla.

The town's Instituto Morelos secondary school partly collapsed, but school director Adelina Anzures said the earthquake drill held in the morning came in handy.

"I told them that it was not a game, that we should be prepared," Anzures said of the drill. When the quake came, she said, children and teachers rapidly filed out and nobody was hurt.

Many people spent Tuesday night on the streets next to homes that were severely damaged or flattened outright, wrapped in blankets on mattresses dragged outside. In the morning they walked past shattered buildings and picked through what was left.

At a wake in Jojutla on Wednesday for Daniel Novoa, a toddler killed when his home collapsed, family members bent over a white child-size coffin surrounded by a crucifix and images of Mexico's patron, the Virgin of Guadalupe. Alongside was a larger open coffin for the child's aunt, Marta Cruz.

In Atzala in Puebla state, villagers mourned 11 family members who died inside a church when it crumbled during a baptism for a 2-year-old girl. People at the wake said the only ones to survive were the baby's father, the priest and the priest's assistant.