Owami Davies was captured on CCTV footage with a man in south London on the night she vanished.
A top university says it is deeply concerned by the disappearance of a student who vanished over a month ago.
King’s College London student nurse Owami Davies was captured on CCTV in the company of a man on 7 July – the night she was last seen alive.
Three men who were arrested in connection with her disappearance have been bailed until September. A fourth man remains in police custody.
The Metropolitan Police say the case remains a missing person investigation.
Ms Davies was first reported missing by Essex Police on 11 July.
The force said she had left the family home in Chafford Hundred, Grays, on 4 July.
In an updated statement on 16 July, police said Ms Davies was last seen in West Croydon late on 6 July walking along Derby Road.
She was wearing a black jumper, grey jogging bottoms and a grey cap.
After a week of further police appeals a spokeswoman for King’s College London said Ms Davies is a valued member of the university’s community.
She said: “We are deeply concerned about her disappearance, and we continue to hope for her swift and safe return.
“We are keeping Owami, her family, and her friends in our thoughts during this difficult time.
“Our immediate priority is cooperating with the Metropolitan Police in their investigation.”
On Friday, the Met said two men, aged 27 and 23, who were detained on suspicion of murder, have been bailed until September.
A 32-year-old man who was arrested on suspicion of kidnap has also been released on bail until next month.
The force said a 22-year-old man police custody having been arrested on Wednesday on suspicion of kidnap remains in police custody.
Det Ch Insp Nigel Penney said: “We are working hard to find Owami but we really do need the public’s help – our concerns that she may have come to harm are growing with each day that remains missing.
“As a result of extensive CCTV inquiries we have a clearer idea of Owami’s movements, but we still need the public to contact us and tell us what they know.”
On Wednesday, police released CCTV of Ms Davies’ last known movements in West Croydon.
Officers are keen to speak to the driver of a white van that was parked in Derby Road.
Police said Ms Davies and the man she was with there crossed the street “just as the van pulled out”.
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