"It is a very sad time for all involved and we extend our deepest sympathies to the family," Acting Central District Commander Inspector Chris de Wattignar said.
"Police staff make every effort to ensure the safety of those in police custody."
A post mortem will be conducted to establish the cause of death.
An investigation and policy and procedures review is underway and the incident has been referred to the IPCA.
WorkSafe has also been notified.
Support is being offered to the family of the deceased and the police staff involved in the incident .
The matter has been referred to the Coroner.