Hampshire Constabulary are appealing for witnesses and information after a 19-year-old woman reported she was raped in Southsea.
The incident happened at around 10pm on Saturday 29 August in an alleyway off of Clarendon Road.
The woman reported she was in the alleyway when a man not known to her attacked her.
The woman continues to receive the support from specialist officers.
Detective Inspector Emma Crute said: “To able ascertain the exact circumstances of what happened, we have been conducting house to house visits and scoping CCTV in the local area. These enquiries will continue, and we would ask any residents to assist us should they have information that could help.
“This incident took place on a busy Saturday night at the start of a bank holiday weekend and we believe there would have been a lot of people out and about who may have seen something.
“We would like to hear from anyone who was in the area of Clarendon Road on Saturday evening who saw or heard anything, or anyone, suspicious.”
Anyone with information is asked to call 101 and quote 44200333243.
Alternatively, call Crimestoppers on 0800 555 111 and leave information anonymously.