Detectives are investigating a sex attack on a 23-year-old woman as she walked home from a night out in Lancaster.
Police said the alleged incident happened between midnight and 2.30am on Monday, March 3.
Officers said the woman was approached by a man on Ashton Road and sexually assaulted.
Specially-trained officers are supporting her.
Detective Inspector Richard McCutcheon said: “We are trying to establish the circumstances around exactly what has happened and I would ask anyone who may have seen anybody acting suspiciously in the Bridge Road/Ashton Road area of Lancaster between the hours of midnight and 2:30am on Monday to come forward and contact us.
“Even the smallest piece of information could be crucial.”
Contact police on 101 or Crimestoppers anonymously on 0800 555 111.