Inmates at Melbourne's Port Phillip Prison are being questioned after a man was stabbed to death at the jail last night.
Paramedics were called to the maximum security prison, at Truganina in the city's west, just before 7:00pm.
They worked on the 23-year-old man at the prison but were unable to save him.
He was pronounced dead just before 8:00pm.
Police said a number of people had been detained for questioning at the jail but no charges have been laid.
They said investigations were continuing but officers believed the man may have been specifically targeted.
As with all deaths in custody, a coroner will also conduct an investigation.
Authorities have released no further information.
Port Phillip Prison can accommodate more than 1,000 inmates within its 13 units.
