A check-in area was evacuated as a precaution
Two London-bound Eurostar trains were delayed after a passenger reportedly tried to take a World War Two shell on board.
Police were called to Paris Gare du Nord station following the discovery on Sunday morning.
The hub's check-in area in the French capital was evacuated as a precaution, a spokeswoman for Eurostar said.
After the "World War souvenir" was found, two trains bound for the England were held in Paris for a short time.
The Paris to London St Pancras service at 8.13am (7.13am Irish time) was delayed by 20 minutes, while a service an hour later was held up for 30 minutes.