A plastic box containing a fake bomb and a note with "boom" written on it was found on a public footpath.
Six plastic cylinders were discovered taped together in the container, along with a ticking pocket watch, in Paignton, Devon, on Monday afternoon.
A member of the public called 999 and police removed the box and destroyed its contents.
Officers suspect it was linked to Geocaching, a game where players track down clues and hunt for hidden boxes.
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Kingsbridge Police were sent to the footpath between Longmead Road and Dolphin Court Road because officers in Paignton were dealing with other incidents.
A small notebook was found inside the box containing names and dates that people had visited it.
People on social media said the box was "in poor taste" and that police "have enough to deal with without time wasting pranks".
Devon and Cornwall Police removed the plastic box from the area and destroyed it.