Extremists are at work
purposely disrupting the Paris Olympics Opening Ceremony hours before the opening. At a distance from the city, arsonists ignited fires inside the conduits that carry the electrical connectivity for much of the French railway. These were set up at three distinct chokepoints leading into the city; most likely, they were probably not being well monitored since they were much farther away from Paris.
The disruption caused some 7,000 Olympic athletes to be stranded on trains at various railway locations outside of Paris. Another 800,000 people were said to have been inconvenienced in getting to their places within the city and for the opening ceremonies. French Prime Minister Gabriel Atta has delivered a message of commitment to capture the arsonist (https://apnews.com/article/france-trains-olympics-74c9727d33ac86bfc126f98e45cb874f).
The arsonists and other factions will continue to exploit and disrupt the Olympic games in the future. There have been 35,000 police officers deployed during the Olympic games (https://www.cbc.ca/news/world/paris-olympics-railway-1.7276164). The French have deployed a mix of ground and air surveillance devices including drones.