PARIS — Hours before the opening ceremony of the Paris Olympics on Friday, part of France’s high-speed rail network was paralyzed by a “massive attack” that disrupted service for hundreds of thousands of passengers, officials said.

Prime Minister Gabriel Attal said the country’s intelligence services and law enforcement agencies had been mobilized to track down suspects as he warned in a post on X that “the consequences for the rail network are massive and serious.”

France’s national rail network SNFC said in a news release that a series of “coordinated” arson attacks had damaged a number of its facilities and services, while another “malicious act was foiled” on the LGV Sud-Est line connecting Paris and Lyon.

Calling the incident a “massive attack,” it said in an update that at least 250,000 passengers would be impacted on Friday, with 800,000 expected to be affected over the weekend. A sweeping number of services had to be cancelled, it said, warning passengers affected to postpone their travel plans and “not to go to the station.”

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SNCF chairman and CEO Jean-Pierre Farandou told reporters that fiber optic cables at at least three locations had been set on fire. The cables were connected to signal boxes and other rail infrastructure, he said.

The attacks appeared to have been coordinated with the intention of causing massive disruption to the country’s rail network, he added.

Paris’ public prosecutor’s office said in a news release that an investigation had been opened involving charges including damage to property likely to harm the fundamental interest of the nation, which can carry a sentence of up to 15 years’ imprisonment and a fine of 225,000 euro, or around $244,200.

French Transport Minister Patrice Vergriete also took to X, where he said “coordinated malicious acts” targeted several lines and would “seriously disrupt traffic until this weekend.”

In comments aired by French broadcaster BFMTV, Vergriete later said the disruptions appeared to unfold simultaneously and appeared intentional. It was unclear who might be responsible.

One passenger, Maëliss Davy, 23, said she had planned to travel from Paris to Nantes, a city in the Upper Brittany region of western France, for a friend’s birthday on Saturday, but was surprised to receive a message on the SNCF app saying her train had been delayed due to an “act of vandalism.”

Her train was later cancelled altogether, she said, speaking with NBC News over X. “Fortunately I’ve managed to book a train tomorrow morning at a station on the outskirts of Paris,” Davy said. However, she added the train station, Gare Montparnasse, was full of confused, tired “and quite impatient” passengers whose travel plans had also been affected.

There was NBC News Chief Foreign Correspondent Richard Engel witnessed widespread confusion at Gare Montparnasse, with a busy crowd of passengers appearing calm, but eager for updates and answers about their delayed journeys.

SNCF said it was working to restore service following the incident as it urged passengers to postpone their travel plans and “not go to the station.” It said all tickets would be exchangable and refundable and that passengers would be informed of updates via text.

Trains appeared to be back up and running normally at one of Europe’s primary hubs, Gare du Nord, by early afternoon.

SNFC trains were seen coming and going routinely with arrival/departure monitors filled with lines of “on time.”

Separately, Eurostar said in a statement on its website that all high speed trains between Paris and the northwestern city of Lille were being diverted from the high seed line to the slower, classic line.

It said it had mobilized teams stations, call centers, and onboard trains to assist passengers and provide them with updates.

Nancy Ing reported from Paris and Chantal Da Silva from London

This article first appeared on NBCNews.com.

This article was originally published on TODAY.com