Over 50 investigators are working on the sabotage that hit the French rail network on Friday, the same day as the OS opening ceremony in Paris.
So far, no one has taken responsibility for the three deliberate fires that broke out and the cables that were cut on Friday, causing chaos in train traffic, reports le Parisien.
An investigation has been initiated by the Paris Prosecutor's Office and 50 investigators from the military police have been linked to the case. The police's anti-terrorism unit has also been linked, writes Le Monde.
According to the Paris police chief, security has been increased at train and subway stations after the fires.
Samples taken on site have been sent to experts for analysis. Several thousand railway workers are working on repairs and checks of hundreds of cables.
The French state-owned railway company SNCF has called the events a "massive, large-scale attack". According to the company, the fires were coordinated and set at key points for cables that control switches and traffic signals.
According to sources that the newspaper Le Figaro has spoken to, the method used in the attack has previously been used by groups within the extreme left.
The French Transport Minister Patrice Vergriete condemns the actions and calls them "criminal".
France's Prime Minister Gabriel Attal writes on X that "our intelligence services are actively working to find and punish the perpetrators of these criminal acts".