A man has died after being arrested on suspicion of shoplifting from Tesco on Christmas Eve.
The 29-year-old fell ill while being detained at Bury St Edmunds Police station in Suffolk.
He was taken to West Suffolk hospital and pronounced dead at around 11pm on Christmas Eve.
The man, from Bury St Edmunds, was arrested at Tesco in Newmarket on suspicion of stealing from the supermarket.
A spokesman for Suffolk Police said: "A full investigation into the circumstances around the man's death is under way and a post mortem examination will be held in due course.
"As is standard procedure where there has been a death following police contact, the Independent Police Complaints Commission (IPCC) have been informed."
The IPCC has launched an investigation into the incident and said: "IPCC investigators are in the early stage of the investigation and were deployed to the post-incident procedures following a mandatory referral from Suffolk Police.
"The IPCC is in the process of reviewing CCTV evidence and speaking with anyone who had contact with the man or who may have witnessed the incident.
"The man's next of kin have been informed and are being offered support at this difficult time.
"Investigators would like to speak to anyone who witnessed the man interacting with store staff prior to police arrival and his subsequent arrest outside Tesco, Fordham Road, Newmarket, at around 6pm on Christmas Eve."
Anyone with information about the incident can call 101.