With just hours to go until the Opening Ceremony for the Paris 2024 Olympics, chaos has hit the country’s transport network. On the night of Thursday, July 25, a series of fires spread across France’s high-speed rail lines, causing delays, cancelations, and disruptions to the rail system.

The fires were a result of coordinated attacks from arsonists. The reasons behind the sabotage remain unknown, but France’s Minister of Transport Patrice Vergriete has condemned them as “malicious acts” and the chief of rail company SNCF Jean-Pierre Farandou has described them as “premeditated, calculated, coordinated” and said there was a “desire to seriously harm”, according to Sky News.

The attack comes as travelers begin flocking to the city—BBC has reported that more than 250,000 people will be affected by the disruption on Friday, July 26, and up to 800,000 will be impacted over the course of the weekend.

“Due to coordinated acts of vandalism in France, affecting the high speed line between Paris and Lille, all high speed trains going to and coming from Paris are being diverted via the classic line today Friday, July 26,” reads a statement from Eurostar. “This extends the journey time by around an hour and a half. Several trains have been canceled.” Travelers are able to cancel or change their journey for free while the situation is resolved.

Rail systems within Paris appear unaffected, but travelers should note that several Metro and RER stations in the city center have closed for the Opening Ceremony.

The news comes as the rest of the French travel industry sees a standstill. Paris’ three airports will close for the evening of Friday, July 26, and the French government announced a “no-fly zone” spanning a radius of 80 nautical miles during the Olympic Opening Ceremony, from 6:30 p.m. until midnight.

For the most up-to-date information about this year’s Paris Olympics visit our complete guide.

This article originally appeared on Condé Nast Traveller UK.