The Met Police is being investigated after the watchdog learnt officers had previously been in contact with missing student nurse Owami Davies.
The 24-year-old from Essex was last seen on 7 July in Croydon after leaving her family home in Grays, Essex three days prior, and has not yet been found.
She was reported missing to Essex Police by her family on 6 July, with the force later handing the file over to the Met on 23 July.
However, on Saturday, Scotland Yard revealed its officers had spoken to Ms Davies on 6 July, after responding to an address in Croydon to concerns over the welfare of a woman.
Both the police and ambulance service attended and spoke to Ms Davies, who told them she did not want help.
At the time, she had not been marked as a missing person on the police database, and was only established later to be Ms Davies during the investigation to find her.
The Met said it is not investigating the officers in question, and its professional standards body was consulted, adding the Independent Office for Police Conduct (IOPC) requested the matter to be referred to them.
In a statement, Scotland Yard said: “The Met’s Directorate of Professional Standards (DPS) were consulted and as there has been contact with police the IOPC were informed.
“The IOPC has requested the matter be referred to them.
“The officers are not subject to any current investigation by the DPS.
“The interaction recorded on the officers’ body-worn video has been viewed by members of the Independent Advisory Group and Owami’s family to ensure openness and transparency.”
The IOPC said in a statement: “We can confirm that we received a referral on August 5 from the Metropolitan Police Service in relation to contact officers had with Owami Davies in Croydon on July 6, after she had been reported missing to Essex Police.
“We are currently assessing the available information to determine what further action may be required.”
A renewed appeal to find Ms Davies was launched last week, with the British Transport Police saying she could still be using trains in the area.
The Metropolitan Police added: “Owami has been depressed and in the absence of her medication may use alcohol to relieve her depression.”
So far, five people have been arrested as part of the investigation, two on suspicion of murder and three on suspicion of kidnap – all of whom have been released on bail.
Anyone with information should call the incident room on 020 8721 4622, or Crimestoppers anonymously on 0800 555 111.