Terrified passengers were evacuated amid reports of a suspicous package on a Thalys train at the city's Gare du Nord railway station.
The French bomb squad have carried out a controlled explosion following the discovery.
Paris is on high alert following a string of bloody terror atttacks, carried out by Islamist extremists.
It comes after French president Francois Hollande urged children to be “unafraid” as they return to school amid growing fears the barbaric Islamic State (ISIS) has made targeting schools and students its number one priority.
What's happening @EurostarUK @Eurostar — half of Gare du Nord station is closed and this queue is HUGE! pic.twitter.com/1WZBCk7XSI
— geo-fleur (@geo_fleur) 4 сентября 2016 г.