The French government is trying and failing to figure out who is behind the mystery illegal drone flights that are driving Paris crazy

The French drone mystery continues: An unidentified drone has been spotted flying over a "sensitive military site" near Paris, AFP reports.

There have been weeks of intermittent nighttime flights in the French capital. There were two consecutive nights of flights back in February, with the unmanned aerial vehicles (UAVs) spotted hovering over multiple famous French landmarks.

And then at least 10 reports were made of mystery drone flights late on March 3. The authorities have sworn to crack down on the flights and arrest those responsible - flying UAVs over urban areas at night in France is strictly forbidden.

"We need to be very vigilant on this, we're going to have to be extremely careful," said a government spokesperson. "The day that we find the people who are doing this, there will be penalties ... We will find them, sooner or later."

This most recent sighting is over a "sensitive military site" near Paris. It is a naval communications centre for France's submarines across the globe. Once again, there's no indication of who is behind the flights.

Drones have previously also been spotted near other sensitive French sites. In November, UAVs were sighted near nuclear power stations, putting the French government on high alert. The Independent believes a "campaign by anti-nuclear campaigners is... the most likely explanation."

The US secret service is also involved. After the American Embassy was targeted, the agency is now "consulting" with Parisian authorities over the mystery.

There have been arrests - but they haven't helped. First they arrested three Al Jazeera journalists, who were operating a drone in order to produce a news segment on the drone mystery. On Friday, authorities announced they had detained four more journalists, also planning to fly a drone in Paris to report on the flights.

A couple was also arrested on Sunday night after flying a drone over Versailles, according to Sputnik News. They claim they "only wanted to take photographs of the world-famous palace at night," and there's not yet any indication if they are connected to the sightings elsewhere.

But they don't fit the description of the operators previously seen by witnesses: Three men have previously been spotted with one of the drones and speeding off with a black car, eluding police capture.

A spokesperson told reporters that the French government isn't concerned about a potential security risk, despite the illegality of the flights. "There is nothing to worry about," they said. But tensions remain high after a massacre at the offices of Charlie Hebdo left 12 dead in January - and one of the mystery drones has been sighted close to the magazine's offices.