Three inmates in hospital and 20 involved in two incidents at Parc Prison in Bridgend
Three prisoners have been taken to hospital from Parc Prison in Bridgend following an "altercation".
G4S, the private company that runs the prison, said their injuries are not life threatening.
An air ambulance attended the site but was not needed.
A separate incident involving around 20 prisoners also took place on Friday night.
G4S said the incident was resolved safely with the help of His Majesty's Prison and Probation Service.
It said no officers were injured.
In a statement G4S said "those involved will receive the strongest possible punishments, including criminal prosecution".
Ten inmates have died at the prison since 27 February 2024.
Families of inmates held protests outside the prison earlier this week demanding answers over the recent deaths.
Speaking to ITV Cymru Wales, a current inmate last month described the prison as a "war zone".
A former worker at the Bridgend prison also told ITV they felt unsafe, while another claimed they were only searched once in a decade while working there.
G4S responded to these claims by saying safety is a priority, and it has a zero-tolerance approach towards drugs and uses a range of tactics to root them out and prevent them coming into the prison.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know...