Police are keeping an "open mind" on whether a man who was found with serious injuries in a Leicester underpass was the victim of a crime or of an accident.
The 38-year-old Asian man, whose name has not been released, is in a critical but stable condition in a specialist head injuries unit at Nottingham's Queen's Medical Centre.
However, he is still too poorly to tell officers how he came to be injured.
A passer-by found him lying injured in an underpass at the junction of Burley's Way and Church Gate, in the city centre, at 2.30am on Sunday.
Detective Constable Denise Reidy said: "The victim was found unconscious in the pedestrian underpass by a member of the public.
"There were a number of people in the area around the time of the incident and we would urge anyone who hasn't spoken with the police to come forward.
"Officers have viewed CCTV images which capture the man walking along Churchgate.
"We would ask anyone who recalls seeing the man or the incident itself to contact us.
"We are keeping an open mind as to how the incident occurred."
The man was wearing a white, short sleeved polo shirt, jeans and black shoes.
The underpass and surrounding area were cordoned off throughout Sunday as officers carried out a forensic examination of the scene.
Contact Det Con Reidy on 101 or Crimestoppers, which is anonymous, on 0800 555 111.
