Four men have now been arrested on suspicion of murder in connection with the disappearance of a missing student nurse.
Owami Davies, 24, left her home in Grays, Essex, and was last seen just after midnight on Derby Road in West Croydon on 7 July.
On Wednesday a 22-year-old man became the fourth person arrested on suspicion of murder, the Metropolitan Police said. Three other men aged 32, 27 and 23 all remain in custody.
Police released images of Ms Davies on the night she was last seen in a shop and CCTV of her walking in Derby Road.
Officers want to speak to the driver of a white van that was parked in Derby Road, saying Ms Davies was with a man and crossed the road just as it pulled out.
They say the van driver would have had a good opportunity to see them both clearly and are appealing for this possible witness to come forward.
Speaking at New Scotland Yard on Wednesday, Owami’s mother Nicol Davies said: “It is obvious that someone out there has seen something, someone out there knows something, someone out there heard something.
“I am begging, I am asking for the public’s help, from the people, to say if you know, if you have heard or seen her, or she passed you, please speak up. All we really want is to find her, all we really need is for her to come home or to know her whereabouts
“I sit here as a desperate mother at the mercy of anyone that knows or heard something to help me find my baby, that’s all I’m asking, just help to find her.”
She added: “Or her, if she’s somewhere and hears this, to please come home.”
“We miss her so much, her brothers and myself miss her, need her.
“We are not complete, we just want her to come home and, again, if she is listening she should know she’s not in trouble.”
Detectives have also extended the search to a property on Derby Road where the student was said to be last spotted.
Police say she was in a “vulnerable state” when she was last seen and urged Croydon residents to check their sheds and outbuildings for anything suspicious.
The Metropolitan Police said the disappearance remains a missing person investigation but said detectives from the Met’s specialist crime command are now leading enquiries to locate the 24-year-old in the “complex” probe.
Detective Chief Inspector Nigel Penney from the Met’s Specialist Crime Command leads the investigation and said:
“While a further arrest has been made, this remains a missing person investigation and our priority is, and has always been, finding Owami.
“I would continue to appeal to anyone who has information about Owami’s whereabouts to please get in contact with my team. If you don’t feel comfortable speaking to police, then you can call the independent charity Crimestoppers – they will not ask for your identity and will not trace your call.”
Mr Penney added: “We are working hard to find Owami but we really do need the public’s help - the longer she is missing the more we worry that she has come to harm.
“As a result of extensive CCTV enquiries we have a clearer idea of Owami’s movements, but we still need the public to contact us and tell us what they know. We would obviously like to speak to the driver of the white van that passed Owami in Derby Road, but anyone with information should call.”
Officers have asked anyone with information about Owami’s whereabouts to call police on 101 or tweet @MetCC quoting reference 22MIS025307.
Alternatively, contact the Missing People charity in confidence on 116 000.
