He said "military assistance" has been added since the sighting to toughen the airport's anti-drone stance and that extra police officers and equipment had been added at Heathrow.
Heathrow staff are working with the Metropolitan Police and all flights have been grounded "as a precaution", an airport spokesperson said.
She said: "As a precautionary measure, we have stopped departures while we investigate".
'We apologise to passengers for any inconvenience this may cause'.
Drone exclusion zones around British airports will be extended and operators made to register under new rules announced after drone sightings wrought havoc at London's Gatwick in the run-up to Christmas.
The UK's busiest airport had said it is working with the police after the device was spotted.
More than two weeks after operations were suspended at London Gatwick for reports of a drone sighting, a similar situation affected service through London's Heathrow Airport.
While another, said: 'Sitting on a plane at Heathrow.
However, it is important to note that a landing or departing plane usually travels between 150and 10 miles per hour, and as drones usually only go about 150 metres high, a strike at that speed is not likely. At present the law state that if a drone endangers the safety of an aircraft it is a criminal offence and carries a prison sentence of up to five years.
While another said: 'Citizens of the United Kingdom should be rather anxious that the presence of a real or imaginary flying helicopter toy can outwit and bring an entire airport to a standstill'.
Many passengers took to Twitter on Tuesday evening to express disbelief that a suspected drone sighting had once again left them stranded, many stuck on the runway.
The disruption resulted in about 1,000 flights being cancelled or diverting and affecting 140,000 passengers.
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