Coastguards were scrambled for a night-time search following the sighting of a white flare.
The sighting – indicating someone may be in distress – was made in the area of Freshwater Bay, Portland, on Saturday night.
It prompted a search by Portland Bill Coastguard Rescue Team.
A team spokesman said: "On arrival we spoke to the first informant and gathered information of the sighting.
"The team split into two search teams – the first search team worked from Portland Bill - north, and the second from Cheyne Tip - south. They searched the shoreline and cliff top, meeting in the middle then retracing their footsteps.
"With the search complete to the best of our abilities under torchlight and nothing found, the team was stood down and returned to station."
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