Flights from London’s Heathrow Airport were suspended for about an hour on Tuesday evening after a drone was sighted nearby, Reuters reported. The Metropolitan Police received reports of the drone at about 5.05 pm local time (10.35 pm Indian time) on Tuesday.

“We are responding to a drone sighting at Heathrow,” said airport authorities. “As a precautionary measure, we have stopped departures while we investigate. We apologise to passengers for any inconvenience this may cause.”

However, arriving planes continued to land at the airport.

About an hour later, authorities confirmed that flight operations had resumed. Heathrow is the busiest airport in Europe, followed by Gatwick, where a drone sighting last month affected flight operations.

The police said they were carrying out extensive searches around the Heathrow area to identify individuals responsible for the operation of the drone. “We are deploying significant resources – both in terms of officers and equipment – to monitor the airspace around Heathrow and to quickly detect and disrupt any illegal drone activity, some of which are as a result of learning from the incidents at Gatwick,” said Police Commander Stuart Cundy, adding that military assistance was deployed as well.

The Gatwick Airport remained closed for more than a day on December 21 after repeated drone sightings. Police had said there had been more than 50 sightings of the drones in 24 hours from when the runway was first closed. The armed forces were also called in to investigate the incident.