Officials at the Delta Fair in Memphis where eight riders were hurt said they were told by first responders that there were no visible injuries.
Media outlets reported that fair officials didn't learn the injuries' extent until the riders were taken to a hospital.
In a statement Sunday, officials apologized for initially downplaying the incident. Among the injuries were a fractured leg, wrist, and collarbone.
The incident happened Saturday on the Moonraker. Fair safety director Matt Snyder said the ride's computer detected a problem and immediately began safety shutdown.
As the ride stopped spinning and began to descend, the operator panicked and pressed a manual override button that released safety restraints before it settled into its cradle.
Some riders fell into metal bars or slid out of their seats.