Two inmates have spent around an hour on the roof of a prison van at HMP Doncaster.
It is understood the pair were being driven in the vehicle before managing to climb on top when it stopped at the category B men's jail on Friday.
They were eventually brought down and are now being transferred to a high-security prison.
A Ministry of Justice spokesman said: "Two prisoners gained access to the roof of a van at HMP Doncaster for a short period of time on Friday December 30.
"This incident was quickly resolved and there was no impact on the prison regime."