Arsonists attacked France’s high-speed rail network early Friday, setting fires that paralyzed train travel to Paris for some 800,000 people across Europe, including athletes heading to the opening ceremony of the Olympic Games.

Targeting remote locations far from the capital, the apparently coordinated attacks sought to cut off rail routes into the city from all directions. The fires were predominantly set in pipes containing critical signaling cables for the system known as the TGV.

There were no reports of injuries. Paris Mayor Anne Hidalgo said the damage would not affect the ceremony in which 7,000 Olympic athletes were due to sail down the Seine past iconic Parisian monuments such as Notre-Dame Cathedral, the Louvre Museum and the Musee d’Orsay.

Fires were reported before dawn near the tracks on three separate lines, causing widespread disruptions. Another arson attempt, in the south in Vergigny, was thwarted by rail agents who scared off several suspects.

French authorities did not publicly comment on who might have carried out the attacks or why; none of them said the sabotage was directly related to the Games.

Prime Minister Gabriel Attal said intelligence services were mobilized to find the arsonists, whose attacks he described as “premeditated” and “calculated.”

The evidence indicates “a desire to seriously harm” the French people, said the CEO of national railway company SNCF, Jean-Pierre Farandou, who estimated the number of customers affected at 800,000. “The places were especially chosen to have the most serious impact, since each fire cut off two lines.”

The rail company said in a statement Friday evening that it would ensure transport for all Olympic delegations, without elaborating. It stepped up ground and air surveillance, including with 50 drones.

Prosecutors in Paris opened a national investigation, saying the crimes included property damage threatening the nation’s “fundamental interests” and could carry prison sentences of up to 20 years.

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