At least 49 people were killed when a powerful, 7.1-magnitude earthquake rocked Mexico, on Tuesday, toppling buildings in the capital.
The preliminary toll from the authorities looked certain to rise, however, as it covered only regions close to Mexico City but not the capital itself, where 20 million people live.
The US Geological Survey said the quake’s epicentre was seven kilometres west of Chiautla de Tapia, in the neighbouring state of Puebla.
In Mexico City, emergency crews and hundreds of volunteers were digging through the rubble of collapsed buildings looking for survivors and bodies.
The quake, which occurred in the early afternoon, hours after city authorities had conducted an earthquake drill, caused most of its damage in the centre and south of the sprawling city.
Several buildings were reduced to debris and cars were flattened by falling masonry.
Scenes of chaos permeated the city, with traffic jammed to a standstill and anxious people running between the vehicles, as ambulances tried to make headway, sirens squealing.
Emergency officials warned people in the streets to avoid smoking because of the risk of igniting gas leaking from ruptured pipes.
In several locations, people were seen clambering on buildings that were now crumpled stone and tangled metal to seek survivors and bodies.
The disaster immediately recalled the 1985 quake in which more than 10,000 people died, escalating panic among the population.
Patients were evacuated from a hospital in the adjoining Roma district, wheeled out on beds and wheelchairs as staff set up makeshift wards outside.
Mexico’s president, Enrique Pena Neto, said on Twitter, he had ordered the evacuation of damaged hospitals “and the transfer of their patients to other medical facilities.”
He said he was to hold an emergency coordination meeting after overflying the disaster zone.
At one collapsed building in Roma, dozens of people clawed at the rubble as they waited for the arrival of heavy machinery to move the heavy chunks of stone. Officials called out for more volunteers, and for water.
Unconfirmed social media posts suggested the city’s international airport had closed because of damage.
Mexico’s stock market was also shut because of the quake.