"We could hear all the sirens and you could smell the smoke as the train went past the site, " he said in a submission to CNN's iReport.

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The danger was compounded by an overhead power cable, which broke loose and fell on the roof of the rear car, causing further arcing and a large amount of smoke inside the train.

BBC: Metro train fire

And the lights went off and smoke started filling the train car.

CNN: Six killed in Washington-area Metro train collision