At least five drones were seen flying over central Paris landmarks throughout the night and police were unable to catch thier operators, a security source told AFP Tuesday.
While the first drone was spotted near the French capital's US embassy, the Eiffel Tower, the Place de la Concorde and the Invalides military museum "were also flown over" in the hours before dawn.
"It could be a coordinated action but we don't know for now," said the unidentified source, who "We did everything to try and catch the operators but they were not found," another source involved in the investigation added.
This is not the first instance of mysterious drones crossing France's skies. On January 20, an unmanned aircraft was seen over the presidential palace in Paris and some 20 drones were witnessed above nuclear power plants.
The most recent case however is the unique in that, according to the security source, "there have never been so many drones appearing in one night."