Police have confirmed they are treating an incident in Beverly Westwood on Thursday 26th April, as a suspected serious sexual assault.
Several officers attended an area of land close to the racecourse after a woman was spotted in a "very distressed state" in woodland.
A large police cordon remains in place as detectives continue to investigate.
Detective Chief Inspector Craig Nicholson said:
Humberside Police believe this is an isolated incident and not related to any other ongoing investigations.