The woman was walking on Southsea Common toward the Pyramid Centre, close to the road junction of South Parade and Jack Cockerill Way, on Monday 3 August at around 9.45pm when she was attacked by an unknown man.
As a result of the attack the woman suffered significant injuries.
This is a complex investigation, and enquiries have also now revealed that the Police are looking at the possibility of two suspects.
Officers are working hard to investigate this incident and continue to appeal for any information the public may have which could help identify the offenders.
A 19-year-old man, who had previously been arrested on suspicion of sexual assault in connection with this incident, is no longer being treated as a suspect and will face no further action.
Detective Inspector Matt Gillooly said: “We understand that these sorts of updates will cause increased anxiety but please be reassured that we are continuing to investigate this case thoroughly and are following a number of complex enquiries.
“It is important that we keep you updated with these developments, and we thank the community for their ongoing support and understanding.
“There continue to be extra patrols on Southsea Common and the surrounding areas, and our officers welcome you to approach them with any concerns. We are doing all we can to identify these men, and keep Portsmouth safe.
“If you were in the area of Southsea Common in the evening of 3 August we ask you to cast your mind back and try to think of anything unusual that stood out to you.
“Temperatures had been high that day and as a result the common was very busy, this was also the weekend the circus were setting up. At the time of the offence the sun was setting and it was dark.
“Did you see two or more men acting suspiciously that night? Perhaps you saw a lone man standing near an area of shrubbery who looked out of place.
“One offender has been described as white with facial hair. He was also described as wearing a dark baseball cap, a dark top with a zip, and a blue surgical facemask.
“If you know of anyone matching this description, or saw anyone matching this description with another man, please get in touch. The information you have might seem small but could prove significant to the investigation.
“We are keen to trace anyone driving on Clarence Esplanade, Jack Cockerill Way, South Parade, Clarence Parade between 9.30pm and 11:30pm who had dash cam recording.
“We would like to remind people to remain vigilant, especially when walking alone in the dark. Try to stick to busy, well-lit areas, stick with friends, and look after each other.”
Phone 101 and quote Operation Outward, or the reference 44200292589.