The state Fire Marshal's office said Sunday that the brother and sister had been on a ride called "the Zipper." It is a huge oval frame that spins like a Ferris wheel with free-flipping cars.
The teens, ages 13 and 15, were getting off the ride Saturday evening when it went in motion, throwing them from the car and dropping them 15 feet.
The fire marshal's office says a preliminary check didn't reveal any mechanical problems with the ride.
Members of the St. Helena Parish School Board told The Advocate of Baton Rouge that they were working to determine who authorized the fair to be held on school grounds.