Trains to and from Paris have been cancelled, an area evacuated and part of the main ring road temporarily closed after an unexploded World War Two bomb was found on tracks leading to Gare du Nord station.
Eurostar services at Gare du Nord were scrapped for the day, after the 500kg bomb was found on tracks in the Paris suburb of Saint-Denis during overnight work.
Homes with windows in a 500m (1,600ft) radius of the bomb were evacuated and part of the Paris circular périphérique was shut as the clearance operation took place.
French Transport Minister Philippe Tabarot said local rail services at Gare du Nord would not resume until late afternoon at the earliest.
Tabarot said on Friday morning that a bomb disposal team was on the scene and there was nothing to worry about. “If we get the green light from the police chief in the coming hours, part of the service could – and I mean could – start up again after 16:00 (15:00G),” he said.
Eurostar said it expected services to return to normal on Saturday.
The bomb was discovered 200m away from the busy Paris périphérique, about 2.5km (1.5 miles) north of Gare du Nord, Europe’s busiest train station.
A nearby short northern stretch of the ring road and the A1 motorway were shut around Porte de la Chapelle. Traffic jams were recorded on 218km of roads in the Paris region.
Authorities in Saint-Denis said there were six schools and a care facility for elderly people inside the evacuation zone, but they were not at risk, because they did not have windows overlooking the area.
Eurostar services were running normally between Brussels and Marne-la-Vallée to the east of Paris as well as trains between London and Brussels and London and Amsterdam.
High-speed TGV trains into Gare du Nord were also badly hit, although some services were diverted to Gare de Lyon in Paris.
The railyards around occupied Paris were regular targets for British and American bombers during World War Two, the BBC’s Hugh Schofield in Paris reports.
Eurostar said passengers would be able to exchange their tickets for free to travel at another date or time in the same class, subject to availability.
“Eurostar will run two additional trains [on Saturday]: a train leaving London for Paris in the morning, and a train leaving Paris for London in the afternoon,” it said in a statement.
Queues were beginning to form by 08:30 GMT at St Pancras train station in London as passengers tried to work out what they could do.
One group was approaching the front of the line after a two-and-a-half hour wait.
Their 07:00 GMT train was cancelled and they planned to travel to Lille and make a three-hour bus journey to Paris.
Jess Sayer from Norwich told the BBC on Friday morning that she was stuck in Paris with her husband and best friend after celebrating her 40th birthday on Thursday.
“We’re frantically on our phones trying to find out what to do,” she said, explaining they had not been able to book a train for Saturday via the website.
“We just tried to get a flight. All the flights are booked up so at the moment we are completely stuck in Paris with no way of getting home,” she said. “Do we get a hotel and risk trying to get the Eurostar home tomorrow? Or look into ferries?”
Her friend, Sarah Fitzgerald, said she was trying to get back to London to help her family prepare for a funeral on Monday.
The Paris cancellations coincided with the middle of Paris Fashion Week and meant that personal shopper Anna Griffiths was unable to travel to Paris for a function.
“We work with all of the designer brands, and Chloé Fashion House had invited me to Paris for their show and a showroom event and a big dinner tonight.”
Ivana Koralek told the BBC she had decided to cancel a trip to see her elderly mother and nephew in France.
She said she had been unable to rebook for three weeks’ time because ticket machines in the station did not offer the discount she had originally received.
Karen Hamblin, from Chester, had travelled to London on Thursday evening to catch a Friday train to Paris for a three-day getaway to celebrate her husband’s birthday.
She said she was told at about 07:00 that their train was cancelled.
“As we were effectively stranded, we have decided to transfer our ticket and travel to Lille,” she said. “Lunch in Lille and [we’ll] then work out how to get to Paris from there!”