A seven-year-old boy was airlifted to hospital following a serious incident at Lightwater Valley theme park near Ripon, north Yorkshire.
The child was taken to Leeds General Infirmary, the Yorkshire Air Ambulance said, following the incident at around 11:30am on Thursday.
The boy was conscious when police arrived. His condition is not thought to be life-threatening, North Yorkshire police said.
The ride has been closed.
Unconfirmed reports say youngster fell off the Twister rollercoaster. One witness wrote on Twitter that the child fell “face down” 20 to 30ft.
Officers are still at the scene.
Lightwater Valley said in a statement on its website: “We can confirm that following an incident on one of our rides this morning, a child is receiving treatment at a local hospital.
“Emergency services have confirmed the child was conscious when they arrived at the scene and his condition is not believed to be life threatening.
“The ride remains closed at the current time but the rest of the park is still open.
“We will issue an update as soon as we have any more information.”
North Yorkshire Police said: “Police were called to reports of a medical incident involving a child at Lightwater Valley theme park near Ripon at 11.30am today.
“Officers are currently at the scene. Further updates will be provided when available.”
North Yorkshire Fire and Rescue Service confirmed they attended the incident but could not provide any further detail.
This piece has been updated to reflect that the victim is aged seven and not six.