LONDON (AP) — London's Heathrow Airport suspended flight departures as a precaution Tuesday after a reported drone sighting that came just three weeks after a rash of drone sightings shut London's Gatwick Airport.

The suspension of takeoffs from Heathrow, one of the world's busiest airports, was announced shortly before 6 p.m. on Tuesday.

London's Metropolitan Police said it received a report about a drone "in the vicinity of Heathrow airport" at about 5:05 p.m. Police say they are working with airport officials to investigate the sighting, which is still unconfirmed.

The report follows the pre-Christmas shutdown of London's Gatwick Airport for parts of three consecutive days due to reported drone sightings. The Gatwick closure led to more than 100,000 people being stranded or delayed, the worst-ever drone-related disruption at an international airport.

The person or persons responsible for the drones that shut down Gatwick have not been located and no group has claimed responsibility.

British officials used sophisticated military gear to get Gatwick back in operation, and aviation authorities said that equipment could be deployed at other British airports to deter drone intrusions. It was not clear if it had been put in place yet at Heathrow.

Heathrow served 78 million passengers in 2017, with 81 airlines flying to 204 destinations in 85 countries around the world. Its most popular destination is New York.