(AP) — All seven people injured when a boat on a ride at an Ohio amusement park accidentally rolled backward down a hill have been treated and sent home.

The Cedar Point amusement park says operators stopped the Shoot the Rapids water ride Friday evening after the accident, which occurred on the ride’s first hill. It says park police, medical technicians, ride operators and park visitors helped passengers off the boat.

Cedar Point officials won’t say how the boat landed after rolling downhill. They say six of the seven boat passengers were treated at the park and the other was treated at a hospital.

Cedar Point is in Sandusky, along Lake Erie between Cleveland and Toledo. It bills itself as the best amusement park in the world.

The accident is being investigated.