The accident happened at Yellow School - Memorial Drive Presbyterian Church just after noon.
According to the Memorial City Fire Department, preschool students at the 240 block of Blalock Road were conducting some type of science experiment outside when a flash blast occurred.
Of the 12 students who were injured, 11 of them suffered burns, one student was trampled and six of them were taken to the hospital. All of the students are 3 years old, a fire official said.
"It was an experiment that went wrong. There was a brief moment of flame and it was put out fairly quickly," church business administrator Bob Giles told ABC13.
As parents and grandparents picked up children who were not injured, some of the kids told Eyewitness News that they were involved in some type of color-changing fire experiment.
"Fire was changing colors and the last one wasn't working, so we put it a little bit more, and then it exploded," said Kate Earnest, a 5-year-old who was part of the group that participated in the experiment. "That's how the other kids got burned, and they were crying."
The victims were taken to Children's Memorial Hermann Hospital in the Texas Medical Center for treatment. Five of the children have been released, and one remains hospitalized in good condition.
Crews from Houston and Memorial Village were called to the scene. The fire marshal and police are investigating the accident.
Parents have been notified about the incident. The other students at the school were not injured, according to Memorial Village police.
"We love these children. This is our church. We're praying for them," Giles said.
On its website, the Texas Department of Family and Protective Services offers a tool to let parents verify licensing and research previous incidents at child care centers.
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