Desperate parents and rescue workers have pulled through rubble in a floodlit search for dozens of young children feared buried under a Mexico City school destroyed by the country’s most lethal earthquake in a generation.

Among the twisted concrete and steel ruin of the Enrique Rebsamen school, soldiers and firefighters found 22 dead children and two adults, while another 30 children and 12 adults were missing, President Enrique Pena Nieto said.

The magnitude-7.1 shock killed more than 200 people – nearly half of them in the capital – on the 32nd anniversary of the 1985 earthquake that killed thousands, and less than two weeks after a powerful tremor killed nearly 100 people in the south of the country.

Mexico’s Government said the death toll had been revised down from 248 to 216.

Chaotic scenes at school collapse

There were chaotic scenes at the school as parents clung to hope their children had survived.

“They keep pulling kids out, but we know nothing of my daughter,” said 32-year-old Adriana D’Fargo, her eyes red after hours waiting for news of her seven-year-old.

Three survivors were found at around midnight (local time).

“Relatives of Fatima Navarro,” one soldier shouted through cupped hands at the school the Coapa district in the south of the city. “Fatima is alive!”

A woman walks past a collapsed building after a 7.1 earthquake, in Jojutla, Morelos state, Mexico. Photo: AP

The earthquake toppled dozens of buildings, broke gas mains and sparked fires across the city and other towns in central Mexico. Falling rubble and billboards crushed cars.

Parts of colonial-era churches crumbled in the state of Puebla, to the south of the capital, where the US Geological Survey (USGS) located the quake’s epicentre.

As the earth shook, Mexico’s Popocatepetl volcano, visible from the capital on a clear day, had a small eruption.

On its slopes, a church in Atzitzihuacan collapsed during mass, killing 15 people, Puebla Governor Jose Antonio Gali said.

Tens of thousands of people ran into the streets in panic, and millions lost electricity when the quake struck around lunchtime.

Sirens blared as first responders rushed through the streets of Mexico City, and people scrambled amid the ruins of buildings, searching for survivors.

Devastating images from Mexico City. pic.twitter.com/RpF7sUq31s

— Jorge Guajardo (@jorge_guajardo) September 19, 2017

Este video muestra el colapso de parte de un edificio de la Secretaría del Trabajo. No tengo ubicación exacta. pic.twitter.com/CSsvHc6DC6

— Enrique Acevedo (@Enrique_Acevedo) September 19, 2017

Mexico City Mayor Miguel Angel Mancera said 44 buildings were severely damaged or destroyed. Several major gas leaks and fires occurred.

The quake hit only hours after many people participated in earthquake drills around the nation on the anniversary of the devastating quake that killed thousands in Mexico City in 1985.

“A drill at 11:00am and an earthquake at 1:00pm,” 23-year-old student Valerie Perez said. “This is the most powerful thing I have ever seen in my life.”

Dangerous rubble causing slow progress

Interior Minister Miguel Angel Osorio Chong said search efforts were slow because of the fragility of rubble.

“It has to be done very carefully,” he said. “Time is against us.”

Mexico City’s international airport said it had suspended operations while officials checked for structural damage.

US President Donald Trump said on Twitter: “God bless the people of Mexico City. We are with you and will be there for you.”

The Department of Foreign Affairs and Trade said it was contacting Mexican officials to determine whether any Australians had been affected.

Australian witness

Australian Peter Davies, who lives in downtown Mexico City, was at home when the quake struck and hurried out of his six-storey building as quickly as he could.

“I was running down stairs, it probably took me a couple of minutes and the quake … was still shaking when I got out to the street for probably a minute-and-a-half or two after I first left my apartment,” he told the ABC.

“I saw a lot of buildings that had suffered structural damage, I saw buildings were cracked and later this afternoon I saw a site where a building collapsed on the other side of downtown, about four minutes from where I live.”

Rescuers, firefighters, policemen, soldiers and volunteers remove rubble and debris from a flattened building after a deadly Mexican earthquake. Photo: AFP

He said people in the city were “anxious and afraid”, with fears of gas leaks and residents wary of going back to apartment buildings that may yet collapse.

Earthquakes of magnitude seven or above are regarded as major and are capable of causing widespread heavy damage.

Power was cut to 3.8 million customers, the national electricity company CFE said.

It was the second powerful earthquake to hit Mexico this month. Another quake on September 7 in southern Mexico killed at least 98 people.

Video captures building exploding after a 7.1 Earthquake strikes Mexico City. https://t.co/3th6ePbFRc

— ResistantCultur (@NonymousAndy84) September 19, 2017

Rescuers erected signs asking for silence at some collapsed buildings as they strained to hear for signs of life beneath the rubble.

At least one survivor was pulled from a collapsed building in the city’s busy Condesa neighbourhood, and another person was rescued from a six-story apartment building nearby.

Hospital patients were also evacuated into the streets in their beds, adding to the confusion.

Hospitals were evacuated, with patients treated in the streets. Photo: AP

In Cuernavaca, a city in Morelos that is a popular destination for weekend visitors from Mexico City, there were reports on local radio of people trapped beneath collapsed buildings.

Mexican TV and social media showed cars crushed by debris.

“We got out really fast, leaving everything as it was and just left,” said Rosaura Suarez, as she stood with a crowd on the street in Mexico City.

-ABC with agencies