France’s state-run power firm EDF on Wednesday said unidentified drones had flown over seven nuclear plants this month, leading it to file a complaint with the police.

France's state-run power firm EDF on Wednesday said unidentified drones had flown over seven nuclear plants this month, leading it to file a complaint with the police.
  
The unmanned aircraft did not harm "the safety or the operation" of the power plants, Electricite de France said, adding that the first drone was spotted on October 5 above a plant in deconstruction in eastern Creys-Malville.
  
More drone activity followed at other nuclear power sites across the country between October 13 and October 20, usually at night or early in the morning, EDF said, adding that it had notified the police each time.
  
Greenpeace, whose activists have in the past staged protests at nuclear plants in France, denied any involvement in the mysterious pilotless flight activity. But the environmental group expressed concern at the apparent evidence of "a large-scale operation", noting that drone activity was detected at four sites on the same day in October 19 -- at Bugey in the east, Gravelines and Chooz in the north and Nogent-sur-Seine in north-central France.