Police, firefighters and ordinary Mexicans dug frantically through the rubble of collapsed schools, homes and apartment buildings early Wednesday, looking for survivors of Mexico's deadliest earthquake in decades as the number of confirmed fatalities climbed to more than 200.

The death toll has fluctuated since the earthquake hit, estimates have ranged from 217 to nearly 250.

Adding poignancy and a touch of the surreal, Tuesday's magnitude 7.1 quake struck on the 32nd anniversary of the earlier temblor that killed thousands and came just two hours after earthquake drills were held across Mexico to mark the date.

A man is rescued from a collapsed building in the Condesa neighborhood after an earthquake struck Mexico City, killing more than 200 people. (Pablo Ramos/Associated Press)

One of the most desperate rescue efforts was at a primary and secondary school in southern Mexico City, where a wing of the three-storey building collapsed into a massive pancake of concrete floor slabs. At the scene, journalists saw rescuers pull at least two small, sheet-covered bodies from the rubble.

Volunteer rescue worker Dr. Pedro Serrano managed to crawl into the crevices of the tottering pile of rubble that had been Escuela Enrique Rebsamen. He made it into a classroom, but found all of its occupants dead.

'We can hear small noises'

"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.

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

Rescuers, firefighters, policemen, soldiers and volunteers remove rubble and debris from a flattened building in search of survivors.

A mix of neighbourhood volunteers, police and firefighters used trained dogs and their bare hands to search through the school's rubble. Reports swept through the crowd of anxious parents outside the gates that relatives in 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 airspaces remained.

Rescue the top priority

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 reported by the federal civil defence agency. Pena Nieto had earlier reported 22 bodies found 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 moving to provide help as 40 per cent of Mexico City and 60 per cent of nearby Morelos state were without power. 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."

A friend of the family helping to clear rubble walks inside the collapsed home of Peregrina Vera's 73-year-old grandmother Faustina, which was destroyed in a magnitude 8.1 earthquake on Sept. 7, in Juchitan, Oaxaca state, Mexico. (Rebecca Blackwell/Associated Press)

People across central Mexico already had rallied to help their neighbours as dozens of buildings tumbled into mounds of rubble. 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 blocking traffic.

Dust-covered and exhausted from digging, Carlos Mendoza, 30, said two people were pulled alive from the ruins of a collapsed apartment building in the Roma Sur neighbourhood during a three-hour period.

'This is ugly, very ugly'

"When we saw this, we came to help. This is ugly, very ugly," he said, gesturing at the destruction.

Blocks away, Alma Gonzalez was in her fourth-floor apartment in the Roma neighbourhood when the quake pancaked the ground floor of her building, leaving her no way out — until neighbours set up a ladder on their roof and helped her slide out a side window.

A damaged car is seen outside a building after an earthquake in Mexico City on Tuesday. (Claudia Daut/Reuters)

Mancera said 50 to 60 people were rescued alive by citizens and emergency workers in the capital.

In a statement, Canada's Foreign Affairs Minister Chrystia Freeland said Canada is prepared to help Mexico as needed and they aren't aware of any Canadians killed in the quake.

"It is with sadness that we learned of the devastating earthquake in Mexico this afternoon. Canada sends its condolences to families and friends in mourning, and hopes for a speedy recovery for the injured. To date, we have no reports of Canadian casualties," Freeland said.

117 dead in Mexico City

The official Twitter feed of agency head Luis Felipe Puente said 117 dead had been counted in Mexico City and 72 in Morelos state, which is just south of the capital. It said 43 were known dead in Puebla state, where the quake was centred. Twelve deaths were listed in the State of Mexico, which surrounds Mexico City on three sides, and three in Guerrero state.

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

People remove debris from a damaged building after a quake hit Mexico City on Tuesday. (Alfredo Estrella/AFP/Getty Images)

Throughout the day, 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.

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

'I think it's human nature'

Where a six-storey 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.

A woman is assisted after the quake in Mexico City. (Yuri Cortez/AFP/Getty Images)

"We are young, we didn't live in '85, but we know that it's important to come out to the street to help," said her sister Victoria.

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

Earthquake drill, then the real thing

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

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

Falling debris from a damaged building crushed this car in Mexico City. (Alfredo Estrella/AFP/Getty Images)

Buildings also collapsed in Morelos state, including the town hall and local church in Jojutla near the quake's epicentre. 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.

Unrelated to earlier quake

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

The U.S. Geological Survey said the magnitude 7.1 quake hit at 1:14 p.m. local time and was centred near the Puebla state town of Raboso, about 123 kilometres southeast of Mexico City.

Much of Mexico City is built on former lakebed, and the soil can amplify the effects of earthquakes centred hundreds of kilometres away.

The quake appeared to be unrelated to the magnitude 8.1 temblor that hit Sept. 7 off Mexico's southern coast and also was felt strongly in the capital.

U.S. Geological Survey seismologist Paul Earle noted the epicentres of the two quakes were 650 kilometres apart and said most aftershocks are within 100 kilometres.

Gustavo Serrano, BuzzFeed Mexico's social media editor, posted this video on Twitter:

En el piso 38 en pleno Reforma. <a href="https://t.co/zuCIke0kc9">pic.twitter.com/zuCIke0kc9</a> —@gooz25

(CBC has not verified the video above or the video below.)