An initial inquiry into July's rollercoaster crash at the Alton Towers theme park in Staffordshire has concluded that it was an "isolated incident" due to component failure.
The Health and Safety Executive, which is not expected to publish its full report for several months, said a problem with the coupling mechanism of the Runaway Mine Train was responsible for the crash, which injured 29 people.
A spokeswoman for the HSE said its inquiry had found that the train's operator pressed an emergency stop button to bring the ride to a gradual halt after the coupling failed.
The spokeswoman explained: "The front and rear of the train carriages separated, the back remaining in the tunnel and the front went up an incline and rolled back and impacted with the back section."
The initial report found that the impact would have occurred at a relatively slow speed and that the ride had a valid safety certificate and had undergone proper maintenance checks.
The spokeswoman noted: "It appears to be an isolated incident."
