Among the buildings damaged was the nearby Concepción Arenal School. A teacher from the school who did not want to give her name said several students had been injured. She said windows were blown out, with shards of glass flying a considerable distance.
The local director of education told Cuban media that five students were injured in the blast.
“It’s shocking,” said Ms. Díaz, whose daughter attends the school but was unharmed by the blast. “It’s really very tough.”
State media reported that children were evacuated to the Capitol in the wake of the blast, and officials said later that students would be able to attend another facility starting Monday. Among those hospitalized were 14 children, the authorities said.
A nearby church was also badly damaged.
“The walls fell down completely. The roof of the church caved in,” said Mr. Morales, who was a parishioner. “All the windows, there wasn’t a single one left — not in the church and not in the Martí Theater that’s in front.”
As rescue workers moved in, Mr. Morales said he watched people being pulled from the rubble. At least three were dead.
“They were destroyed,” he said. “You could see a lot of blood.”
The Cuban Communist Party newspaper, Granma, said on Twitter that the explosion occurred “while liquefied gas was presumably being moved from a truck.”