Milan’s Malpensa Airport was temporarily closed by a drone flying near a terminal, forcing four planes to be redirected to nearby airports.

The airport operator SEA said Monday that the airport was closed for about a half hour after the drone was sighted around midday. Three flights landed at Milan’s Linate airport and a fourth in Turin.

Malpensa underwent a similar closure last month when a drone was spotted from the control tower several kilometers (at least two miles) away. Police were investigating both incidents.

Drone sightings have caused major chaos at London airports in recent months. Rules by the Italian Civil Aviation Authority specify that drones are not permitted to fly within 5 kilometers (3 miles) of airports.