There were at least 20 children killed in their primary school
The death toll continues to rise following a major earthquake in central Mexico.
The 7.1 tremor has killed more than 200 people and forced thousands on to the streets.
The number of those killed is fluctuating and has been changed several times as rescue efforts continue, with the last official death toll indicating 216 people have died.
At least 20 children were among those killed after their school collapsed.
Thirty of their classmates and eight adults are still missing in the building, which like dozens of others has been turned into rubble.
Two adults were also killed when the primary school Colegio Enrique Rebsamen collapsed in Mexico City, said the country's President Enrique Peña Nieto, who visited the scene.
The quake hit Mexico hours after preparation drills were held on the anniversary of a devastating 1985 earthquake that killed more than 5,000 people in Mexico City.
At the school, TV pictures showed rescue teams working late into the night, using picks, shovels and their hands as well as heavy lifting gear in an attempt to find survivors.
Education officials said 25 bodies had been recovered but three were pulled out alive.
Relatives said they had received a WhatsApp message from two girls inside.
"They keep pulling kids out, but we know nothing of my daughter," said 32-year-old Adriana D'Fargo, whose seven-year-old remains missing.
Volunteer rescue worker Pedro Serrano (29) a doctor, managed to crawl into a classroom but found its three occupants dead.
"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," he said.
Mexican President Nieto, after visiting the school, appealed for calm, saying: "The priority at this moment is to keep rescuing people who are still trapped and to give medical attention to the injured people."
Earlier, panicked workers fled from office buildings and clouds of dust rose up from the crumbling facades of damaged buildings after the quake struck.
As many as 44 buildings collapsed in Mexico City, according to mayor Miguel Angel Mancera.
Amid the screams and shock, terrified parents ran to cradle their children in the worst affected areas of Roma, Condesa and Doctores.
Many others, in areas where multi-storey blocks had concertinaed flat, dug with their bare hands as they waited for specialist machinery to arrive.
Speaking from New York - where he is attending the UN General Assembly - Foreign Affairs Minister Simon Coveney said he learned of the earthquake with 'deep sadness'.
In a statement, he said: "I wish to extend my condolences to the people of Mexico and in particular to the families of those who lost their lives or have been injured as a result of the earthquake.
"Those who may still be trapped under fallen buildings are very much in all of our thoughts and we pray that the brave men and women of the local emergency services may be able to rescue them. As of now, we have no indications to suggest that any Irish citizens have been affected."
President Michael D Higgins has sent condolences to Mexican President Nieto, and to the people of Mexico.
In a letter, President Higgins offered his condolences, on behalf of the people of Ireland, on the "tragic loss of life" as a result of the earthquake in central Mexico.
The president also recalled the earthquake that hit Mexico's Puebla State earlier this month - and expressed the solidarity of the Irish people with those affected by the tragedies.
The US Geological Survey (USGS) said the quake was centred near Raboso in Puebla state, 123km southeast of Mexico City, but the shaking in the capital was almost as intense.
At patches of rubble where floors had pancaked on top of one another, cheers and applause occasionally broke out as rescuers pulled people to safety.
At others, signs saying "silencio" were held up as emergency personnel thrust themselves into hollows in the debris as they tried to hear if anyone was trapped.
One of those rescued, Alma Gonzalez, said: "It was a very hard hit that went down and then I went to find my child and I couldn't so I started to WhatsApp (Phone App) and I was trapped on the third floor... and the people in the house next door helped me get out with a ladder... I am just grateful to God that we are here for something."
Officials asked people not to smoke in the streets of Mexico City - which has a population of 20 million - warning of possible ruptured gas pipes.
Mexico City International Airport suspended operations, while electricity and phone lines were down in parts of the capital.
As night fell, thousands of people remained on the darkened streets, afraid to return to their homes in fear of aftershocks.
The earthquake came less than two weeks after an 8.1 magnitude tremor in southern Mexico killed at least 98 people.