Police are investigating the serious assault of a 29-year-old woman in Richmond, Nelson.
Police say the assault occurred around 1.30am on Sunday 18 July and the woman did not require medical attention at the time.
"However, this was an extremely traumatic experience and she has been offered support through Victim Support services," police said in a statement.
Police want to hear from residents and anyone else who was in the general area of Cautley Street and Hunt Street prior to and around this time, and may have seen or heard anything that may assist in their investigation.
The offender is described as being tall, with a solid build and wearing dark coloured clothing at the time, police say.
There will be a noticeable police presence in the area over the coming days as the investigation continues.
"We will be carrying out a canvass of all homes in the area and we are particularly interested in obtaining any CCTV footage."
If anyone has information relating to the incident, they can contact police on 105 quoting file number 210720/9908.
Information can also be provided anonymously via Crimestoppers on 0800 555 111.