US National Transportation Safety Board vice chairman Bella Dinh-Zarr has told reporters that an investigation into Thursday's train crash "will continue here on scene for seven to 10 days".
She said the train was operating in a "push-pull configuration", in which the locomotive can be driven at either end, and confirmed retrieval experts will remove the event recorder - which tracks speed, braking and other data - from the rear of the train on Thursday night.
Officials had earlier confirmed the train driver was injured and taken to hospital, but was later released.
They did not provide details of his injuries, but said he was cooperating with investigators.
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A top temperature today of 13 Celsius (55F).
Mr Trump tweeted that Mr McMaster has done "an outstanding job & will always remain my friend." He said MrBolton will take over on April 9.
The committee wants a more stringent interpretation of air quality laws and for noise estimates to reflect a range of possible flight paths.