Independent Police Complaints Commission (IPCC)
A South Wales man died after being taken into police custody following his arrest on suspicion of damaging a vehicle.
The Independent Police Complaints Commission (IPCC) said attempts were made to resuscitate 23-year-old Lee Donovan, from Newport, after he was found collapsed in his cell at Pontypool police station.
A forensic medical examiner pronounced Mr Donovan dead at the station, an IPCC spokesman said.
Mr Donovan was arrested in Newport but taken to Pontypool as Newport police station was closed for refurbishment.
The watchdog is now awaiting the results of forensic tests before the cause of death can be confirmed.
IPCC Commissioner for Wales Tom Davies said: "My sympathy and condolences go to Mr Donovan's family and friends.
"I have decided that an independent investigation is appropriate in this case to find out what happened after Mr Donovan's arrest and while he was in custody.
"The IPCC investigation will report to the coroner to help inform the inquest into the circumstances of Mr Donovan's death."
An inquest date has not yet been arranged.
Ifti Manzoor in the Police Prosecutions team at Irwin Mitchell said: "Any death in custody is tragic - it is imperative that there is a full and comprehensive investigation to determine how the death occurred and what procedures were put in place to monitor this man whilst in custody. The police officers actions of the arrest and subsequent detention should be fully scrutinised at any future inquest."