A suspected mortar bomb has been found in St Ouen's Bay.
Police say whoever found the shell picked it up and took it home, from where they reported the find.
A bomb disposal officer has been sent to collect it.
The force is reminding people not to collect or remove any World War II remnants because they could be dangerous.
"Our Island is steeped in history, and while these discoveries can be fascinating, they can also be dangerous.
"This doesn't often happen but if you come across anything suspicious, leave it where it is and contact us on 612612.
"We will take your call, request for photos and location (we request for What 3 Words for precise location if it is located on a beach).

Early voting opens in Jersey's general election
Third successive day of record May heat expected
DFDS withdraws Jersey-Guernsey ferries
"Tropical nights" forecast for the Channel Islands
Les Amis nursing home on track to open this autumn
Candle-lit evening at St Brelade's Bay Beach to remember loved ones
How to have 'safe and enjoyable' Jersey beaches for summer
Appeal after woman grabbed by throat in nightclub