More than 200 people have been killed in an earthquake in central Mexico - including at least 21 children whose school collapsed on them.
Dozens of buildings has been reduced to rubble, forcing thousands of volunteers and emergency personnel to scrabble through the debris in a frantic search for survivors.
The 7.1-magnitude quake hit hours after preparation drills were held on the anniversary of a devastating 1985 earthquake that killed more than 5,000 people in Mexico City.
The death toll has yo-yoed as authorities have struggled to keep up with the number of bodies being brought into hospitals and morgues.
But the latest official figures put the number of dead at 216, with fears it could rise further as more bodies are discovered.
At the collapsed Enrique Rebsamen school in Mexico City, 25 bodies - all but four of them children - have been recovered, the federal education department said.
Thirty children and eight children are still missing.
A volunteer rescuer managed to squeeze into a classroom after teams created a cavity into the ruins of the building. He found four bodies, but no survivors.
There have been reports of trapped children send WhatsApp messages from underneath the rubble .
President Enrique Pena Nieto, who has visited 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."
The US Geological Survey (USGS) said Tuesday's quake was centred near Raboso in Puebla state, 76 miles (123km) southeast of Mexico City, but the shaking in the capital was almost as intense.
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Panicked workers fled from office buildings and clouds of dust rose up from the crumbling facades of damaged buildings as the quake struck.
Amid the screams and shock, terrified parents ran to cradle their children in the worst affected areas of Roma, Condesa and Doctores.
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 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.
The earthquake came less than two weeks after an 8.1 magnitude tremor in southern Mexico killed at least 98 people.
Amid the latest quake, the Popocatepetl volcano near the capital had a small eruption, flattening a church on its southern slopes and killing 15 people attending a mass.