Bus and tram drivers are being urged to contact cops if they think they may have seen missing 12-year-old Tia Sharp.
Tia did not have her young person's travel card with her but some bus and tram drivers let children travel without one.
Detective Chief Inspector Nick Scola said: "I am appealing for any bus or tram drivers in the Croydon area who recognise Tia's description to contact us. Of course if Tia herself is able to contact her family or the police, we urge her to do so."
"We are currently examining CCTV; at this time we have found no trace of Tia on the footage examined thus far, but this is an ongoing process which will take time.
"We have spoken to Tia's family and some of her friends and Tia has never gone missing before and it is extremely out of character for her not to return home or contact her friends or family.
"There has been a lot of activity on Twitter from Tia's friends and, whilst we would want to ensure that images of Tia and details of her disappearance are spread far and wide, we would urge people using social media to include the Incident Room number rather than their personal numbers. We have received a number of purported sightings but none are confirmed as Tia at this time."
Mr Scola repeated appeals for information and said he was particularly keen to hear from anyone in The Lindens area of New Addington who had information.
Mr Scola said: "Tia is white, 4ft 5in and slim, and was wearing FCUK glasses. She was dressed in a yellow bandeau top over a white bra with visible cross straps, light grey leopard print leggings and black and pink Nike high top trainers.
Police believe Tia had a small amount of cash with her, but no travel card and she did not have her mobile phone. She is known to frequent the Croydon, Mitcham and Wimbledon areas. Anyone who has seen Tia or knows of her whereabouts should call Merton Police on phone number 101, quoting reference 12MIS025216.