The destruction revived horrific memories in Mexico on the anniversary of another massive quake in 1985, the disaster-prone country's deadliest ever.
One of the most gut-wrenching scenes was at the Enrique Rebsamen primary school on Mexico City's south side, whose three floors collapsed into one, trapping students and teachers inside.
Twenty-one children and five adults were killed, said Major Jose Luis Vergara of the Mexican navy, who was coordinating a rescue effort that involved hundreds of soldiers, police, civilian volunteers and rescue dogs.
He said another 30 to 40 people remained trapped inside, while 11 children have been rescued so far.
Emergency workers found a teacher and a student alive beneath the rubble and are trying to get them out, he said.
But the situation was precarious. Late into the night, part of the wreckage collapsed as rescuers continued their search.
Local media reports said soldiers had administered oxygen to one trapped child through a tube.
President Enrique Pena Nieto, who rushed to the site, warned the death toll could rise.
"Unfortunately, many people have lost their lives, including children, in schools, buildings and homes," he said in a national address.
The devastation struck across a swath of central states and the death toll as of early Wednesday was 248, the head of the national disaster response agency, Luis Felipe Puente, said on Twitter.
In addition to Mexico City, people were also killed in Puebla, Morelos, Mexico state and Guerrero, said Interior Minister Miguel Osorio Chong.
