Four boys were arrested on suspicion of assault after a teenager was airlifted to hospital at Alton Towers.
A 13-year-old, 14-year-old and two boys aged 15, all from Liverpool, were arrested following the incident at the Staffordshire theme park on Thursday.
A boy from Dudley, aged 15, suffered facial injuries and is in stable condition in hospital, Staffordshire Police said.
Detectives said the four boys remain in custody.
Alton Towers said it was a matter for the police.
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