Emergency teams were called after a flare was found on Littlehampton beach on Saturday afternoon (January 19).
Littlehampton Coastguard officers were tasked to assess and collect the flare, which had been handed into the local RNLI station.
According to the Coastguard, the item was from Greece and expired more than 10 years ago.
It was made safe for transport and stored in a mitigation cage before being taken to a secure storage site, said a spokesperson for Littlehampton Coastguard.
They said: If you do find a flare on the coast we ask that you do not touch it, or move it in any way, take note of its position and immediately call 999 for the Coastguard.
“Flares are a form of explosive and can be dangerous, especially if they are old or damaged, or mis-handled.
“Coastguard Officers are specifically trained to identify and work with flares, we have the correct PPE to keep us safe.”