The Smiler rollercoaster at Alton Towers has been closed after a wheel fell off and hit someone on the ride.
A spokeswoman said a wheel came off and hit a guest on the ride which "caused some bruising".
Alton Towers said an investigation would be carried out to find out when the ride could re-open.
The injured person was looked after by park staff and did not need to go to hospital.
The Smiler was shut for four days in July after a piece fell off the track and it closed again in August due to a "technical issue".
The spokeswoman said: "All of our rides and attractions are expected to meet extremely high standards."
"We are sorry for any disappointment the ride's temporary closure caused our visitors but the health and safety of all of our visitors is our absolute priority," she said.