A fifth man has been arrested over the disappearance of student nurse Owami Davies, with the Met Police renewing their appeal for information a month on from the last confirmed sighting of her.
The police have now arrested five people - two on suspicion of murder and three on suspicion of kidnap.
The most recent arrest was a 27-year-old man held on suspicion of kidnap on Saturday.
Four of those arrested have since been released on bail.
Ms Davies, 24, was last seen in the early hours of 7 July as she walked along Derby Road, West Croydon.
Police have also been informed of a second, but unconfirmed, sighting of Owami also on 7 July. This was at 7am in Clarendon Road, Croydon.
She had left her family home in Grays, Essex three days earlier.
Detective Chief Inspector Nigel Penney, who is leading the investigation, said: "This is a complex ongoing investigation involving a significant number of officers.
"We are working tirelessly to follow every line of enquiry, including extensive CCTV trawls, as we continue to search for Owami.
"We are now a month on from the last confirmed sighting of her. I cannot imagine what that time has been like for her family. We continue to provide them with whatever support we can.
"I am grateful for the help we have received from the public so far, but I must again appeal for anyone who has information - however insignificant they believe it might be - to get in touch."
The Met's Specialist Crime Command is leading the investigation to establish what has happened to Owami.
Anyone with information has been urged to contact the incident room on 020 8721 4622.