The French national rail company SNCF said Friday that high-speed lines were hit by several “malicious acts” that heavily disrupted traffic on the day of the high-risk Olympics opening ceremony.

Lines in the west, north and east of France were affected, SNCF announced. Trains to neighbouring Belgium and to London under the English Channel were also affected.

Government officials denounced the incidents hours before the opening ceremony of the Paris Olympics, which are happening around France, though there was no immediate sign of a link to the Games.

National police said authorities are investigating what happened. French media reported a big fire on a busy western route.

Many French families are also heading on summer vacation Friday.