us. >> the wheels the train wheels went off the track. and it could be because of a defective rail. it could have been because a wheel broke. metal fatigue sometimes causes these problems. >> that is one of the many things ntsb is going to have to investigate we want to get more input now from another expert who is a railroad safety consultant. we're going to go to him i just want to update our viewers. it is about two hours now since we've heard that this passenger train had detailed. amtrak train detrailed and had no official briefing from first responders, the mayor's office amtrak, or anyone else for that matter. all of our information at this hour has been from those who are on board the train. as i say that amtrak sends out a tweet.