Emergency responders search for passengers following an Amtrak train derailment in the Frankfort section of Philadelphia

Emergency responders search for passengers following an Amtrak train derailment in the Frankfort section of Philadelphia, Pennsylvania, May 12, 2015. An Amtrak passenger train with more than 200 passengers on board derailed in north Philadelphia on Tuesday night, killing at least five people and injuring more than 50 others, several of them critically, authorities said. Authorities said they had no idea what caused the train wreck, which left some demolished rail cars strewn upside down and on their sides in the city’s Port Richmond neighborhood along the Delaware River. REUTERS/Bryan Woolston