'As a precautionary measure, Heathrow Airport has stopped departures and officers based at Heathrow are now investigating the reports with colleagues from Heathrow Airport, ' the force added.
"We are responding to a drone sighting at Heathrow", the airport said.
Heathrow officials said shortly before 6 p.m. Tuesday that flight departures have been suspended as a precaution.
Another said: "Sitting in a flight, doors closed at @HeathrowAirport T5 only to have the pilot announce that we are now on a long queue of aircrafts waiting to take off due to some #drone activity in the airport".
Flights at Heathrow Airport have been grounded after fresh reports of a drone sighting, with passengers venting their frustration on social media.
This latest incident comes just a few weeks after all flights were grounded at Gatwick Airport after it was reported that drones were seen near the site. "We apologies to passengers for any inconvenience this may cause".
A drone flies in Hanworth Park in west London, as a British Airways 747 plane prepares to land at Heathrow Airport behind.
Arriving planes, however, are continuing to land at Heathrow. About 1,000 flights were cancelled or diverted, affecting 140,000 passengers.
Meanwhile, UK government introduced new police powers against drones flown near airports this week.
Following the end to the initial drone-related disturbance at Gatwick, Security Minister Ben Wallace said: "I can say that we are able to now deploy detection systems throughout the United Kingdom to combat this threat".
Police could also fine drone users failing to comply with authorities or present registration to operate a drone up to £100.
The exclusion zone around airports is now one kilometre (half a mile) and this will be extended to five kilometres.