A 35-year-old man has been arrested on suspicion of rape following an attack over the weekend.
The incident, which involved a 35-year-old woman, happened sometime between 9-40pm and 10-15pm at the rear of Exchange Street and Blascomy Way on Saturday.
The woman was on her way back from a night out in Colne when she encountered a lone man smoking a cigarette.
The man may have been disturbed during the attack when someone has been heard speaking further up the backstreet. Police are appealing for any witnesses to come forward.
Detective Inspector Jim Elston said: “This appears to be an opportunist attack on a vulnerable lone woman returning home from a night out.
“This is a vicious crime which has had a significant impact on the victim who is being supported by specially trained officers”.
“I would appeal to anybody that saw a man acting suspiciously in the area around the time of the offence or anyone that thinks they may have witnessed this incident to contact police as a matter of urgency.”
Officers are inspecting CCTV footage and carrying out house to house enquires. Anyone with any information is urged to contact 101 or Crimestoppers on 0800 555 111.