The Metropolitan police confirmed that they were investigating reports of a drone sighting over the runway this evening, at the airport's busiest time of day.
It comes just weeks after Gatwick Airport descended into chaos amid several reported drone sightings before Christmas.
The Gatwick closure led to more than 100,000 people being stranded or delayed, the worst ever drone-related disruption at an international airport.
It prompted Chris Grayling, the Transport Secretary, to seek a change to the law to thwart such attacks, giving police and airports new powers to shoot down, catch and jam drones.
The latest development at Heathrow came shortly after 5.30pm on Tuesday evening. Many passengers took to Twitter to express disbelief that a drone sighting was once again leaving them stranded, many stuck on the runway.
A Heathrow spokesman said on Tuesday evening: "We are currently responding to a drone sighting at Heathrow and are working closely with the Met Police to prevent any threat to operational safety.
"As a precautionary measure, we have stopped departures while we investigate. We apologies to passengers for any inconvenience this may cause."
- with Daily Mail