Nelson police are urging anyone who was near a Bishopdale road in the early hours of the morning on December 7 to get in touch.
Police would particularly like to speak to anyone who may have seen a woman walking along Waimea Rd, followed by a man walking on the road toward Bishopdale.
The woman was assaulted around 2.15am on the Nelson Rd.
A 20-year-old man was arrested and charged with abduction and aggravated assault four days later, on December 11.
While the man has been remanded in custody, local police would still like to speak to any witnesses.
Nelson police are also interested in speaking to anyone approached on Friday, December 6, by a man wearing either a green camouflaged top or a red-hooded top.
Anyone with any information should contact Detective Constable Jesse Gaskell from Nelson Police on 105, file reference number 191208/8799.
Information can also be provided anonymously via Crimestoppers on 0800 555 111.