A 28-year-old man died shortly after being found unconscious at Mount Carmel Hospital on Saturday afternoon, the police said.
The victim, a resident of Sliema, was found in his cell at the hospital's forensic ward around 4pm. He was rushed to Mater Dei Hospital for treatment but died on arrival.
A magisterial inquiry has been ordered. Police are investigating the cause of the death.
An autopsy is expected in the coming hours.