An investigation has begun into a suspected sex attack on a woman on a canal towpath in Burnley, police said.
A Lancashire Police spokeswoman said the alleged assault, close to Thompson Park. was reported by the woman at about 01:45 GMT.
The spokeswoman added: "Officers are currently trying to establish exactly what has occurred. No arrests have been made as yet."
Patrols have been stepped up to "reassure" residents.