The wiggling fingers of a young girl trapped in the rubble of her collapsed school in Mexico City raised hopes among hundreds of rescuers working furiously Wednesday to try to free her — a drama that played out at dozens of buildings toppled by the powerful earthquake that killed at least 245 people.

The death toll rose after Mexico City Mayor Miguel Angel Mancera said the number of confirmed dead in the capital had risen from 100 to 115. An earlier federal government statement had put the overall toll at 230, including 100 deaths in Mexico City.

Mancera also said that late Wednesday two women and a man had been pulled alive from a collapsed office building in the city's centre.

But it was the rescue operation at the Enrique Rebsamen school, where 25 people including 21 children perished, that was seen as emblematic of Mexicans' rush to save survivors before time runs out.

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Rescue workers search through the rubble for students at Enrique Rebsamen school after the earthquake in Mexico City. (Edgard Garrido/Reuters)

Helmeted workers spotted the girl buried in the debris early Wednesday and shouted to her to move her hand if she could hear. She did, and a rescue dog was sent inside to confirm she was alive. One rescuer told local media he had talked to the girl, who said her name was Frida.

Hours later the crews were still labouring to free her, as images of the rescue effort were broadcast on TV screens nationwide. Workers in neon vests and helmets used ropes, pry-bars and other tools, frequently calling on the anxious parents and others gathered around to be silent while they listened for any other voices from beneath the school.

Microphone in the rubble

At one point, the workers lowered a sensitive microphone inside the rubble to scan for any noise or movement. A rescuer said they thought they had located someone, but it wasn't clear who.

"It would appear they are continuing to find children," said Carlos Licona, a burly sledge-hammer wielding volunteer who came to help in any way he could. Asked if that made him optimistic, he said, "I hope so."

But by late Wednesday night, workers had not been able to get to her, although workers found four corpses in the rubble, volunteer rescue worker Hector Mendez said. Mendez said cameras lowered into the rubble suggested there might be four people still inside, but it wasn't clear if anyone beside the girl was alive.

Amid the devastation are more hopeful stories too. One woman said her 10-year-old child escaped the school while the stairs were breaking apart. After escaping the crumbling building, the child ran back in to help rescue a friend who was still inside.

"It's hard to be happy when so many other mothers are grieving today," the woman told the CBC's Kim Brunhuber near the school. 

Mass rescue effort

It was part of similar efforts at the scenes of dozens of collapsed buildings, where firefighters, police, soldiers and civilians wore themselves out hammering, shovelling , pushing and pulling debris aside to try to reach the living and the dead.

By mid-afternoon, 52 people had been pulled out alive since Tuesday's magnitude 7.1 quake, Mexico City's Social Development Department said, adding in a tweet: "We won't stop."

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A woman with a relative possibly buried under the rubble of a building knocked down by the earthquake awaits news from rescue teams in Mexico City. (Ronaldo Schemidt/AFP/Getty Images)

Among them were 11 people rescued at the Enrique Rebsamen school, where three people remained missing, two children and an adult. Earlier, journalists saw rescuers pull two small bodies from the rubble, covered in sheets.

More than 24 hours after the collapse, the debris being removed from the school began to change as crews worked their way inside: from huge chunks of brick and concrete, to pieces of wood that looked like remnants of desks and paneling, to a final load that contained a half dozen sparkly hula-hoops.

Rabbits and rats

Even as stunning rescues of people continued, such as a man pulled alive from the rubble of a partly collapsed apartment building in northern Mexico City, there was also a rescue of animals Wednesday.

Mexico City police said rescue workers clearing wreckage from a collapsed medical laboratory in the Roma neighbourhood found and removed 40 lab rabbits and 13 lab rats used by the firm that had occupied the building, now a pile of beams and rubble.

City authorities also announced that quake victims staying at city shelters would be allowed to bring their pets with them, and several community groups have started to collect donations of animal food for affected pets.

A helicopter overflight of some of the worst-hit buildings revealed the extent of the damage wrought by the quake: three mid-rise apartment buildings on the same street pancaked and toppled in one Mexico City neighbourhood; dozens of streets in the town of Jojutla, in Morelos state, where nearly every home was flattened or severely damaged and a ruined church where 12 people died inside.

100 killed in Mexico City

The death toll included 100 people killed in Mexico City, 69 in Morelos state just south of the capital and 43 in Puebla state to the southeast, where the quake was centred. The rest were in Mexico State, which borders Mexico City on three sides, Guerrero and Oaxaca states, according to the official Twitter feed of civil defence agency head Luis Felipe Puente.

President Enrique Pena Nieto declared three days of national mourning even as authorities made rescuing the trapped and treating the wounded their priority. "Every minute counts to save lives," Pena Nieto tweeted.

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Rescuers, firefighters, police, soldiers and volunteers search for survivors in Mexico City on Wednesday after a strong quake hit central Mexico the day before. (Yuri Cortez/AFP/Getty Images)

In the town of Jojutla, dozens of buildings collapsed, including the town hall. One building was rocked off its foundations and part way into a river.

Town residents who had spent Tuesday night on the streets next to homes that were severely damaged or flattened outright, wrapped in blankets or on mattresses, walked past shattered buildings and picked through what was left when daylight came

'An ugly and horrible experience'

"It was an ugly and horrible experience. Our house used to be two floors and it ended up ... a total loss. I thank God that my 83-year-old mother, my daughter-in-law with her baby, we all escaped with scratches," said a tearful Maria Elena Vargas, 54, adding that everything they had was in the rubble.

"I hope that the government helps us because this block is destroyed, that they do not just profit from others' pain," Vargas said. "Now we have to lift ourselves up, with or without the government."

At a wake 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.

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Family members attend a wake for toddler Daniel Novoa and his aunt, Marta Cruz, earthquake victims in Jojutla, Morelos state, Mexico, Wednesday. (Eduardo Verdugo/Associated Press)

Canadians in Mexico

There are currently 3,320 Canadians in Mexico. Registration with the federal government is voluntary, however, and that figure "may not reflect the actual number," said Philip Hannan, spokesperson for Global Affairs Canada. 

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Volunteers raise their fists asking for silence as they listen to a request for emergency supplies to be taken to another earthquake stricken area, in the Linda Vista neighbourhood of Mexico City, Wednesday. (Rebecca Blackwell/Associated Press)

"As of Wednesday morning, there have been no reports of Canadian casualties," he said. 

In a statement issued Tuesday night, Foreign Affairs Minister Chrystia Freeland said, "The government of Canada is ready to assist Mexico as needed and appropriate."

She stressed that Canadians requiring consular assistance should contact Global Affairs toll-free at 1-613-996-8885 or by email at sos@international.gc.ca.

Mexico's ambassador on devastating earthquake6:23

With files from Kim Brunhuber and CBC News