A natural gas tanker truck lost control and exploded on a highway lined by homes in the Mexico City suburb of Ecatepec early on Tuesday, killing at least 20 people and injuring nearly three dozen, according to the Citizen Safety Department of Mexico State, which surrounds Mexico City.
Officials did not rule out the possibility the death toll could rise more as emergency workers continued sifting through the charred remains of vehicles and homes built near the highway on the northern edge of the metropolis.
Residents pitched in to rescue people from the wreckage of the 5.30am. explosion, crushed and burned cars and shattered homes. Television footage showed plumes of flame shooting out of homes in the pre-dawn darkness.
"It was a thunderous sound. I thought we were all going to die," said Rita Enriquez, 42, a housewife who lives near where the blast occurred. "When we ran out, we saw a car on fire and flames everywhere. Smoke was pouring all over the freeway."
Ms Enriquez said five of her relatives were gravely injured in their concrete slab home along the freeway, though she had no other details as she waited for word outside Magdalena Las Salinas Hospital in Mexico City. Her 15-year-old niece, Wendy Garrido, who was pregnant, was forced to give birth in the aftermath of the explosion, she said.
Cesar Gomez, Mexico state health secretary, said the injured people receiving care at Magdalena had burns over at least 70% of their bodies. He said the teenager and baby survived, but both are in intensive care. More than 20 remained hospitalised at various facilities by Tuesday afternoon, eight in grave condition.
The driver, Juan Olivares, 36, was heading to Mexico City from Pachuca, a city to the north, when he hit the centre divider, said Jose Luis Cervantes, assistant prosecutor for the state of Mexico. The tractor carrying two gas tanks broke apart, with one flying into a house and exploding, killing 15, and another part of a tank hitting a separate house, killing four. Mr Cervantes did not say where the 20th person died. He said the driver may face manslaughter and property damage charges.
"We just pulled burned people, and put out the fire in the houses, but we don't really know what happened," said Rogelio Martinez, a resident of the neighbourhood where the crash occurred.
Speaking in Mexico City, President Enrique Pena Nieto suggested something would have to be done to separate major highways from poor neighbourhoods.
"I have instructed the Transportation Department ... to review the safety conditions on this federal highway in places where structures have been built on the right of way, so that in the near future, work can be carried out to make it safer," Mr Pena Nieto said.