Officers are continuing to investigate an incident that happened on Sunday 10 April in Above Bar Street where a man was found seriously injured at 4am
The man, a 21-year-old from London, suffered serious stab wounds to his abdomen and hand and was taken to hospital.
The man remains in hospital at this time in a serious condition although his injuries are no longer considered life threatening.
Today (April 13), he will be interviewed under caution as part of police enquiries to ascertain the exact circumstances of what happened.
He remains in hospital receiving treatment.
A 19-year-old man from Fareham who also suffered a stab wound has been discharged from hospital and is now in police custody being questioned by officers on suspicion of attempted murder.
Police previously arrested a 21-year-old from Southampton on suspicion of attempted murder.
He had also suffered stab wounds and had been treated at hospital before police questioned him in police custody. He has since been released under investigation.
Police also arrested a 17-year-old boy from Winchester on suspicion of causing grievous bodily harm with intent and attempted murder. He was released under investigation.
Leading the investigation, Detective Inspector Rich Aston said: “Officers investigating the incident continue to review CCTV and are carrying out extensive enquiries in the area and with potential witnesses to understand the exact circumstances of how these men came to be injured on Sunday.
“We continue to have increased patrols in the area and we would ask anyone with information about the incident to come forward if they have not already made contact us.
“If you can assist us with this investigation, please call 101 and quote 442200140497.”