PARIS -- Eurostar trains to London and all trains heading to northern France were brought to a halt Friday following the discovery of an unexploded bomb dating back to World War II near the tracks.

France’s national train operator SNCF said in a statement that traffic would be stopped at the Gare du Nord until mid-morning at the request of police.

“We invite travelers to postpone their trip,” it said.

The Gare du Nord is a major European transit hub, serving international destinations north of France as well as the main Paris airport and many regional commuters.

Bombs left over from World War I or World War II are regularly discovered around France but it is very rare to find them in such a people-packed location.