A 35-year-old man died after being found unresponsive in a police cell less than a day after being taken into custody, the police watchdog says.
Ian Dyche's death has been referred to the Independent Office for Police Conduct (IOPC) by Staffordshire Police.
Mr Dyche, the IOPC said, was arrested at his home in Cannock on 29 April and taken to the town's police station.
The following morning, he was found unresponsive and taken by ambulance to hospital where he died on 8 May.
A post-mortem examination into the cause of Mr Dyche's death was inconclusive, the IOPC said, adding further tests were due.
CCTV from the custody block at Cannock police station is being examined along with body-cam footage from the arresting officers.
IOPC commissioner Derrick Campbell said the investigation was at an early stage and extended his sympathies to Mr Dyche's family.