Detectives are seeking help to piece together events which led to a woman returning home semi-clothed in the early hours of the morning.
The incident happened in East Grinstead when the 44-year old woman had been sitting near the Sainsburys end of Worth Way - a footpath and cycle track in the town - from around 4pm on Wednesday 6 July, drinking alcohol.
At some point during the following 12 hours her lower clothing was removed, and was found nearby, say police.
At 4am the following morning, Thursday 7 July, she then made her way home and the police were contacted.
Detective Sergeant Sian Harding said; “The woman was physically unhurt, and at this stage it is not at all clear what actually happened, but we do not rule out the possibility of a sexual motive or an actual assault of some kind.
“If you were around the Worth Way area between about 4pm on Wednesday afternoon and 4am on the Thursday morning and saw the woman, or saw anything suspicious, please contact us.
“You can email firstname.lastname@example.org or call 101, quoting serial 136 of 07/07.
“Alternatively you can contact the independent charity Crimestoppers anonymously on 0800 555 111 (www.crimestoppers-org.uk)”.