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).

Nowacki wins Jersey’s first Commonwealth Games medal in 36 years
Thousands expected at Havre Des Pas Festival this weekend
Commonwealth Games: Nowacki into 100m breaststroke final
Channel Islands face 'physical' Poland test
Price of heating oil and other fuel increase by more than half in a year
Man jailed for importing nearly £600k worth of cannabis in bumpers of his car
Baby born on Guernsey's Marine Ambulance
Drug trafficker who claimed he was the ‘Accredited Dealer' jailed