“In some cases we can say that they were not drones, but we’re not done with all our questioning and reported incidents. But we should be able to arrive at some kind of result by the end of the week,” a senior police official, Per Engström, told the TT news agency.

Police stressed that they have not yet been able to confirm any of the alleged drone sightings.

In January 2022, police received around 200 drone observations, several close to power plants, within the scope of one week. The lion’s share of them turned out to be nothing but false alarms, with airplanes, helicopters, satellites and masts often mistaken for drones.

“I guess it’s always like this when there’s some kind of mass psychological effect, you start looking like ‘what’s that?’, you look up into the sky more than you usually do and discover that there are lots of things moving around there,” said Engström.

The Armed Forces have been informed of the reports, but are not otherwise involved in the investigation.

It began when four suspected drones were spotted at Arlanda Airport, just north of Stockholm, in the early hours of Monday. Flights were grounded for several hours, although it was the middle of the night so only six flights ended up being redirected to other airports.

After that there were new reports of drones on Tuesday and Wednesday.