A Royal Navy bomb disposal squad has been called to an area near Shopwyke Nurseries, Chichester, where a suspected unexploded device was found.
Shop owner Simon Thomas said a cylinder he thought might be an explosive shell had been found in a box of items at the shop.
Police cordoned off the area and a team from Southern Diving Unit 2 from Portsmouth attended to examine the device.
Leading Diver Dale Magnus said the item was thought to be a detonator cord from a shell which may contain explosive.
The squad intended to safely remove the device and take it away to be examined and x-rayed.
Mr Thomas, who runs a shop at the site called Shopwhyke Chic, selling antiques and collectables, said the object had been found in a box of items left at the business.
The device has been taken away for examination and Shopwhyke Chic and Shopwyke Nurseries are now open for business again after being closed for several hours.