At least seven people were killed, including four babies, when a gas tank truck exploded outside a maternity hospital in Mexico City, officials said.
Many of the victims were injured by flying glass, according to the city's mayor.
Part of the maternity hospital reportedly collapsed due to the force of the explosion.
One official said victims were still likely to be trapped in the rubble.
The blast, which happened on the western edge of Mexico City, sent a pall of smoke above the area.
Emergency crews were at the scene searching for anyone buried under the twisted metal and rubble.
Mexico City Mayor Miguel Angel Mancera told a local television station that at least 54 people had been injured, 22 of them children.
He added that the blast was possibly caused by a leak in the hose carrying gas from the truck to the hospital, the Associated Press news agency reported.