A 35-year-old inmate has died inside the Alexander Maconochie Centre, ACT police say.
A police spokesperson said emergency services were called to the prison after an inmate was found unconscious on Wednesday morning.
Police said ACT Corrections staff members and ACT Ambulance Service paramedics treated the man, but he was pronounced dead at the scene about 11am.
The police spokesperson said officers had informed the man's next of kin of his death.
An ACT government spokesperson said corrections officers provided first aid when the inmate "became unwell". They said attending paramedics were not able to revive the man.
"We acknowledge the grief of the deceased's parents and family, friends and loved ones, and extend our sincere condolences to them," the government spokesperson said.
"It would not be appropriate to comment further."
ACT Policing said an investigation of the circumstances surrounding the incident was underway.
The police spokesperson said the coroner would determine the cause of death, as all deaths in custody were subject to a coronial inquest.
This is the second death in custody at Alexander Maconochie Centre in less than 18 months.
The death of 34-year-old Justin Cordy in March 2023 triggered a critical incident review. The inquest into his death finished earlier this month in the Coroner's Court.