The police helicopter was launched in Norwich after reports of a man indecently exposing himself along a popular cyle and walkway.
Police were searching the area along Marriott's Way close to the Halfords store off Barn Road after the alarm was raised at around 8pm on Friday.
The police helicopter was in the air for around 20 minutes to help with the search for the offender, but he could not be traced.
Police have previously investigated reports of a flasher in the area, along the nearby river bank opposite the Wensum Park area.
Officers are talking to witnesses of the incident in order to get a description of the man and inquiries are continuing.
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