Massive inferno amid explosions near London's Heathrow Airport

Fire crews are fighting a blaze at a warehouse near Heathrow amid reports of several explosions. Photo / Jon Edgar / Twitter

Firefighters are battling a huge blaze at an old coal depot that's sent plumes of black smoke into the sky near London's Heathrow Airport.

Trains have been cancelled from Paddington station after the fire broke out in West Drayton, the Daily Mail reports.

Witnesses reported hearing multiple explosions as 70 firefighters fought the inferno at the storage yard. The cause of the blaze is not yet known.

In a statement, the London Fire Brigade said that a "container, an industrial conveyor belt, 15 vans and three articulated lorries" are currently alight.

Station Manager Jon Holt, who is at the scene, said: "The fire is very visible and is producing a lot of smoke. Residents and businesses in the area should keep their windows and doors shut and drivers should avoid the area if possible."

One witness said on Twitter that her flat shook following the explosions.

Dramatic footage posted online shows smoke filling the sky just north of Heathrow Airport.

A spokesperson for the airport said flights were still operating despite the heavy clouds of smoke blanketing the area.

Rail services out of Paddington station were cancelled for a short time just as the London Marathon came to a close.

National Rail said that Heathrow Express and TfL Rail services were returning to normal, but Great Western Railway services would be delayed or cancelled.

British Transport Police said officers were on scene supporting the fire service with the incident, warning commuters that the fire was impacting services into London Paddington station.

It tweeted: "No services in either direction while emergency services deal with a track-side fire. Alternative routes include Piccadilly Line services."

Great Western Railway services to Reading have also been affected and tickets are being accepted on alternative routes.

Holt said that control officers took more than 55 calls to the fire and around 15 people fled the yard before firefighters arrived.

A Met Police spokesman said officers were assisting with road closures.