The blaze reportedly began at about 1930 GMT in a machine room under a wooden escalator.

The escalator connected the Piccadilly line - one of five underground train routes which run through King's Cross - with the mainline station.

The fire started as the evening rush hour was trailing off but hundreds of commuters were still in the station which is London's busiest.

Many passengers were trapped underground as the escalator went up in flames.

More than 150 firefighters wearing breathing apparatus tackled the blaze and searched for survivors.

But they were not able to bring the main fire under control until approximately 2150 GMT.

It is feared the death toll could reach 40 after a search of the station has been completed.

'Major disaster'

A fire brigade spokesman, Brian Clark, said the scene in the concourse at the top of the burnt escalator was one of total devastation.

Mr Clark said tiles had come off walls and concrete was damaged because of the intense heat.

"The situation there must have been very frightening and that is an understatement," he added.

About 20 people, including four members of the emergency services, have been taken to hospital suffering from smoke inhalation and burns.

The chairman of London Regional Transport (LRT), Sir Keith Bright, has described the blaze as a "major disaster".

Sir Keith said LRT was already implementing a policy to replace old wooden escalators with non-flammable metal ones.

Prime Minister Margaret Thatcher said she was "horrified" to hear of the "dreadful" fire and sent her deepest sympathies to the families of those who have been killed and injured.

The Railway Inspectorate has started an investigation into the blaze and will advise Transport Secretary Paul Channon about ordering an inquiry.

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