Just hours before the Paris Olympics’ opening ceremony on Friday, a “massive attack” paralyzed part of France’s high-speed rail network, disrupting service for hundreds of thousands of passengers, according to officials.

Prime Minister Gabriel Attal announced that the country’s intelligence services and law enforcement agencies were mobilized to find the suspects, warning on X that “the consequences for the rail network are massive and serious.”

France’s national rail operator, SNCF, reported that a series of “coordinated” arson attacks had damaged several facilities and services, and another “malicious act was foiled” on the LGV Sud-Est line connecting Paris and Lyon.

SNCF, describing the incident as a “massive attack,” updated that at least 250,000 passengers would be affected on Friday, with 800,000 more expected over the weekend. Many services were canceled, and passengers were advised to postpone their travel plans and avoid going to the station.

Interior Minister Gérald Darmanin assured that there were no threats to the opening ceremony itself, though the rail attack inconvenienced those arriving or departing by train. He characterized the sabotage as attacks against the French people rather than the Olympic Games.

A significant security operation is in place for the opening ceremony, involving about 45,000 police officers in Paris and 10,000 military personnel in the Île-de-France region—the largest deployment in peacetime. SWAT officers will accompany athletes on boats on the River Seine, navy divers will inspect vessel hulls for explosives, and sonar will detect underwater intruders, with nets set up as entry barriers. The banks and bridges of the river are locked down, and buildings along the ceremony route have been searched.

SNCF Chairman and CEO Jean-Pierre Farandou revealed that fiber optic cables in at least three locations were set on fire, affecting signal boxes and other rail infrastructure.

Preliminary information from French law enforcement and intelligence suggests anarchists or extreme leftist groups are likely responsible for the coordinated sabotage, according to two senior U.S. law enforcement and intelligence officials briefed on the matter. The investigation is ongoing.

The Paris public prosecutor’s office announced an investigation into charges including property damage likely to harm the nation’s fundamental interests, carrying penalties of up to 15 years’ imprisonment and a fine of 225,000 euros (around $244,200).

French Transport Minister Patrice Vergriete also posted on X about the “coordinated malicious acts” targeting multiple lines, predicting serious traffic disruptions through the weekend. He later told BFMTV that the disruptions appeared simultaneous and intentional, though the perpetrators were unclear.

Passenger Maëliss Davy, 23, shared that her planned trip from Paris to Nantes was canceled due to the “act of vandalism.” She managed to book another train from a station outside Paris but described Gare Montparnasse as full of confused and tired passengers.

In Lille, passengers were rushing to get to Paris for the opening ceremony. Tomomi Guillochon, from London, also faced delays and confusion at Gare Montparnasse, where passengers were eager for updates on their journeys.

By early Friday afternoon, Gare du Nord’s services seemed back to normal, with trains listed as “on time.”

SNCF stated all tickets would be exchangeable and refundable, with updates provided via text.

Additionally, the Basel Mulhouse Freiburg Airport in eastern France was briefly evacuated due to a bomb scare, though flights resumed shortly afterward.

Eurostar announced that all high-speed trains between Paris and Lille were diverted to slower lines, with teams mobilized at stations, call centers, and onboard trains to assist passengers.

These disruptions coincide with a recent increase in terrorism and violent incidents in France. A 40-year-old Russian man was indicted for allegedly planning to “organize events likely to cause destabilization during the Olympic Games.” Authorities are also investigating an 18-year-old in connection with a terrorist organization, and another man was arrested on terrorism charges for attacking a taxi driver, following a separate incident where a police officer was wounded in a knife attack in Paris.