Police are investigating an incident involving three prisoners at HMP Full Sutton in Yorkshire.
A Ministry of Justice spokesman said: "An incident involving three prisoners took place at HMP Full Sutton on 26 May from 4.25pm and was successfully resolved at 8.40pm after staff intervened.
"A police investigation is ongoing."
More top news
A revolutionary cancer-fighting machine will deliver proton beam therapy for the first time in the UK.
Low pressure brings cooler, more seasonal weather over the next few days.
Donald Trump has denied making or possessing recordings of chats with his fired FBI chief James Comey, despite hints to the contrary.