Detectives investigating the murder of a man found with fatal stab wounds in the communal hallway of a residential property appealed for anyone with information to come forward today.
The 51-year-old was discovered unconscious and with several stab wounds when police and ambulance workers were called to 67 Elm Grove, Brighton, East Sussex, just after 10am yesterday.
Despite efforts to revive him, the man died shortly afterwards.
Detective Chief Inspector Trevor Bowles, who is leading the major crime branch investigation into the incident, said officers "urgently" needed to trace the murder weapon, believed to be a knife.
He also appealed to anyone who may have noticed an altercation outside the terraced property, which is in a popular student area of the city, to come forward.
Mr Bowles said: "We are beginning to piece together the events which led to the death of this man at 67 Elm Grove. He was stabbed several times in the chest and side of his body.
"We still urgently need to trace the murder weapon. I believe that a knife has been used to commit this murder. Should anyone find a blood-stained knife, please call us. It is vital that we trace this weapon.
"We have spoken to a number of witnesses who are helping to put together exactly what happened and why. But I would urge anyone who saw a confrontation on the doorstep of 67 Elm Grove yesterday to come forward and help us find the killer.
"It is quite likely that the confrontation was visible to passers by who may not have realised its seriousness. The house is a third of the way up Elm Grove on the left-hand side."
One man was arrested at the scene and a second man was held later in Worthing, West Sussex, both on suspicion of murder.
Both have since been released without charge, although one of them is being treated as a "significant witness" to the incident.
A spokesman for Sussex Police said officers have been carrying out "extensive inquiries" into the circumstances surrounding the man's death.
A section of Elm Grove surrounding the property where the man was found was cordoned off by police yesterday along with a cluster of nearby recycling bins.
Specialist police search officers have been scouring the area for a weapon, including checking drains.
A post-mortem examination was taking place at Brighton Mortuary this afternoon.
Anyone with information about the incident is asked to contact Sussex Police quoting Operation Odessa, or Crimestoppers, anonymously, on 0800 555 111.