Texan police have opened an investigation after an officer was caught on camera “body slamming” a 12-year-old girl on a school’s concrete floor.

The footage shows Janissa Valdez thrown to the ground to a chorus of screams of classmates, one of whom shouts, “She landed on her face!”

The pupil’s mother claimed that her daughter “wasn’t moving” and was “knocked out” for a brief moment following the body slam.

The officer involved, named by local media as Joshua Kehm, was suspended following the launch of a formal investigation into the incident, which took place at Rhodes Middle School in San Antonio, Texas.

Authorities from the San Antonio Independent School District admitted that the video was “very disturbing” and police and officials wanted to interview as many witnesses as possible.

Ms Valdez told local media that the officer went at her after believing she was planning to start a fight with another pupil.

"I was going up to her to tell her let's go somewhere else so we could talk but that's when the cop thought I was going at her," Janissa told News4SanAntonio.

Her mother, Gloria Valdez, told the same source: "You could just hear where she hits the ground. And it's nothing but concrete, cement. She wasn't moving. She was just knocked out. I wanted answers and nobody could give me answers.”