A man with blood on him was arrested in Kemp Town after screaming was reported to Sussex Police.
Now officers in Brighton are trying to trace a possible victim of an attack in the street.
The screaming was heard in the Percival Terrace area in Marine Parade at about 7.15pm on Sunday (5 February).
Police went to the scene and arrested a 34-year-old local man in Percival Terrace who had blood on him.
Sussex Police said that inquiries had so far failed to trace any victim or actual witnesses to any offence.
The man was later released on conditional police bail until Sunday 4 March while further inquiries are carried out.
PC Sue Williams said: “From all the circumstances we think it very likely that an assault of some kind had been carried out nearby.
“It’s not clear whether such a victim was male or female, but if you were the victim we would very much like to hear from you, at least to establish that you are safe.
“We also need to hear from anyone who was in the area early on Sunday evening and who saw anything suspicious.”
Anyone with information is urged to call the police on 101 or the independent charity Crimestoppers anonymously via 0800 555111.
