FIREFIGHTERS are battling a huge blaze at a 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 Sunreports.

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 just as the London Marathon came to a close. The incident has caused major train travel disruptions which are expected to continue throughout the day.

A Heathrow Express spokesperson said no trains were coming in or out of Paddington Station as firefighters tackled the blaze.

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.

Mr 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.