An investigation was launched on Friday after several drones flew over France's Ile Longue nuclear submarine base in the Brittany region.
An investigation has been opened and assigned to the military prosecutor's office in Rennes, the Atlantic Maritime Prefecture told French daily Liberation.
The investigation came after it was reported by French media that five drones were detected on Thursday evening flying over the base that houses four nuclear ballistic missile submarines.
The marines reportedly carried out anti-drone strikes and a search operation was deployed.
The drones were small models "that did not pose a threat to sensitive infrastructure," Commander Guillaume Le Rasle, the spokesperson for the Atlantic Maritime Prefect, further told Liberation.
The naval officer also noted that drone overflights in the area are "not common," but there had been "precedents."
