At least six people are now known to have died and scores of others injured in a train crash in Philadelphia.<br /><br /> All seven carriages and the engine of the Amtrak train came off the track while travelling towards New York City.<br /><br /> Authorities say they still do not know what caused the crash, which left about 135 people in hospital. <br /><br /> Robert Sumwalt from the National Transportation Safety Board told a media conference: “We’re looking at the track, the train signals, the operation of the train, the mechanical condition of the train and human performance. <br /><br /> “We are setting up a multi-disciplinary investigation to try to understand the factors that led to this accident.”<br /><br /> The train was carrying some 240 passengers and crew.<br /><br /> US media quote FBI officials as saying there is no indication that the crash was caused by an act of terrorism.
