North Yorkshire Police are hoping social media sharing will help identify the woman but say they cannot say any more about her or the investigation for “operational reasons”.
They said she is not a suspect but may have vital information. Her picture - which shows her sticking out her tongue and sporting a round sticker saying “Adult Admission” - has been shared thousands of times on Facebook and re-tweeted hundreds of time on Twitter.
Police forces around the UK have helped share the message.
A force spokesman said he could not add anything to the message on Facebook, which said: “Officers have issued an urgent appeal to identify a woman they would like to speak to who could have vital information that would assist an ongoing investigation.
“Officers stress that she is a potential witness and not a suspect in any crime.
“It is not known who she is or where she lives and by sharing the appeal on social media, police are hoping that the woman, or someone who recognises her will get in touch.”
The message went on: “For operational reasons we are not able to provide any further details about the investigation, but again stress that she is not a suspect.
“The woman, or anyone else with any information, is asked to contact North Yorkshire Police urgently on 01609 643588 during office hours or 01904 618691, select option 1 and speak to the Force Control Room, any other time. Or email [email protected]”
The message is headlined: “Urgent Appeal”. The Twitter version of the appeals says: “PLEASE RT: We need urgent help to identify this woman. She is not a suspect but may have vital info. She could be anywhere in the country.”