They've also released CCTV images of a man they want to speak to.
Sex Attacker May Have Been In Paisley Town Centre
Detectives investigating a serious sexual assault believe the attacker may have been in Paisley town centre hours before the incident happened.
The 40-year-old woman was attacked in the early hours of Sunday November 27 as she walked along Merksworth Way in the Renfrewshire town.
The attack happened at 2.20am when the woman was approached by a man who pushed her to the ground and seriously sexually assaulted her.
Her attacker ran off in the direction of the airport and the victim was helped help by residents of a nearby house.
Police were called and the woman was taken by ambulance to the Royal Alexandra Hospital in Paisley and released after treatment.
The man is described as white, 5ft 7ins, well-built, with dark spiky hair and an eastern European accent. He was wearing a dark hooded top with the hood up and jeans.
Detective Inspector Louise Harvie, from the public protection unit based at Renfrew, said: "A dedicated team of detectives are carrying out extensive enquiries at the scene as well as within Paisley town centre to find the person responsible for this horrendous attack as quickly as possible.
"From the CCTV footage examined so far, I believe the suspect may have been in Paisley town centre in the hours before the incident took place.''
Police Scotland have appealed to the public to come forward with information.
Ms Harvie added: "If you were in Paisley town centre on Saturday night, please cast your mind back and consider whether you may have seen a man matching the above description.
"We also know that the victim made her way home from the town centre and was on Love Street around 1.20am. Were you near to Love Street around that time? Did you see a woman walking alone or anything suspicious?
"No matter how trivial you think your information may be, please come forward and ensure we can establish the full circumstances of this incident.''
It happened in Broxburn this morning.
It's after their Champions League qualifier.
Police say he suffered a serious facial injury and was taken to Edinburgh Royal Infirmary for treatment.
Most Viewed Pictures On Heart
Recently Played Tracks
To listen live, choose your preferred station:
Now playing: The best feel good music
Deposit £10 to get a £40 Welcome Bonus - That's £50 to play bingo, slots and more!*
Over 50 tracks to make you feel-good. New album out now...
Find your local four day weather report here.
Make Heart the soundtrack to your day and you could be a winner with great prizes up for grabs throughout the day.
Find out more about some of the companies advertising on Heart Scotland- East.