A man died in the early hours of Christmas Day after being found collapsed in Leeds city centre.
Yorkshire Ambulance Service paramedics were called to the 49-year-old man's aid in Sovereign Street at around 2am.
The man, who had not yet been named, was treated by paramedics but pronounced dead at the scene a short time later.
Although his death has been attributed to natural causes, detectives have arrested a teenager on suspicion of robbery.
A West Yorkshire Police spokesman today said: "A post-mortem examination has shown his death was due to natural causes resulting from existing medical conditions.
"As a result of police enquiries into the circumstances surrounding his death, a 16-year-old male was arrested on suspicion of robbery. He was later bailed pending further enquiries."
"Officers are continuing to carry out enquiries and would like to hear from anyone who was in the area and may have seen the victim in company with another male in the time leading to him collapsing."
Anyone with information is asked to contact Detective Sergeant Rob Stabler via 101, quoting crime number 13160753561, or call the independent charity Crimestoppers anonymously on 0800 555 111.