A suspected drone that caused a runway at Schiphol airport to be closed for 45 minutes was probably a balloon, border police have said.

Air traffic was diverted away from the Polderbaan shortly after midday on Saturday after several pilots reported seeing an object flying about 150 metres above the ground.

A police helicopter was sent up to investigate the sightings, but found nothing. The military police force Marechaussee, which is responsible for security at Schiphol, said no drones had been picked up on radar images and the offending item was most likely a balloon.

Planes were ordered to use the Zwanenburgbaan instead until police gave the all-clear at around 1pm.

European airports have been on high alert in the last week for drones, after Copenhagen and Oslo were closed as result of drone sightings.

Denmark said it had been the target of a “hybrid attack” after drones were also spotted above military bases. Prime minister Mette Frederiksen did not rule out the possibility that Russia was behind the “systematic operation”, but Moscow has strongly denied any involvement.

So far this year 22 drones have been reported in no-fly zones above Dutch airports, including Schiphol, compared to 25 for the whole of 2024, police said.