A bomb exploded in a new housing estate after homeowners and businesses were told to evacuate.
The shell was found at around midday on Thursday in a building site north of St Leonards where more than 150 new homes are being constructed.
Homes and businesses near Ashdown House in St Leonards, including a Sainsbury's superstore, were evacuated while police kept the area safe until experts arrived. The Army were called in to make it safe.
The bomb was detonated at the scene and people were allowed back into their homes the same afternoon.
A spokeswoman for the Ministry of Defence said: "We can confirm an Army Explosive Ordnance Disposal team from 11 EOD and Search Regiment RLC was called out to St Leonards at the request of Sussex Police.
“The item found was a 105mm shell of unknown age or origin. It was safely disposed of in situ.”
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