Amtrak train 188 derails
Eigh people were killed and more than 200 injured when an Amtrak train carrying 243 people from Washington D.C. to New York, on the nation's busiest rail corridor, derailed in Philadelphia, May 12, 2015.
In this photo, investigators and first responders work near the wreckage May 13, 2015 of the Amtrak passenger train that derailed late on May 12 in north Philadelphia.
Amtrak Train 188
At a news conference Friday evening, May 15, 2015, NTSB member Robert Sumwalt explained that investigators interviewed two assistant conductors from Amtrak Train 188 who indicated that the train may have been hit by an object. Sumwalt described a circular pattern of damage on the lower part of the windshield.
The NTSB said it wants the FBI to examine damage to the windshield of Amtrak Train 188, to determine if the train may have been struck by a projectile prior to Tuesday night's derailment in Philadelphia.
Amtrak Train 188 victims
This combination photo shows six of the eight victims who were killed by the Amtrak Train 188 crash. Clockwise from top left, Jim Gaines, Justin Zemser, Derrick Griffith, Abid Gilani, Rachel Jacobs and Bob Gildersleeve.
Amtrak train derailment
An aerial view of the derailed Amtrak Northeast Regional Train 188 as investigators and first responders work near the wreckage in north Philadelphia, May 13, 2015.
Amtrak train derailment
Philadelphia Mayor Michael Nutter briefs members of the media near the site of a train derailment accident in Philadelphia, May 13, 2015. Service has been interrupted after Amtrak train 188 derailed in Philadelphia Tuesday night, killing at least eight people and injured more than 200.
Amtrak train derailment
Emergency workers look through the remains of a derailed Amtrak train in Philadelphia, May 13, 2015. Rescue workers sifted through twisted metal and debris from the wreck of the Amtrak train on Wednesday that derailed in Philadelphia May 12, 2015, killing seven people and injuring scores of others, as investigators began reviewing data to determine the cause of an accident.
Amtrak train derailment
Rescuers work around derailed carriages of an Amtrak train in Philadelphia on May 13, 2015. Rescuers continued to comb through the mangled wreckage of the train as the difficult search for possible survivors continued.
Amtrak train derailment
Passengers injured in an Amtrak train derailment and crash, who were bused from New York from Philadelphia, get assistance from the Red Cross at Penn Station in New York, May 13, 2015.
Rescuers on Wednesday combed through the mangled wreckage of a derailed train in Philadelphia after an accident that left at least six dead, as the difficult search for possible survivors continued.
Amtrak train derails
Emergency personnel work the scene of the deadly train wreck in Philadelphia, Tuesday, May 12, 2015.
Amtrak train derailment
An Injured Amtrak passenger, who bused from to New York from Philadelphia, waits at Penn Station in New York, May 13, 2015.
Amtrak train derailment
People arrive at New York's Penn Station from a NJ Transit train on May 13, 2015 in New York City. An Amtrak train crash in Philadelphia late on Tuesday night forced train service to be suspended between New York, Philadelphia and Washington D.C., causing commuters to use NJ Transit, flights and bus services.
Amtrak train derailment
The Amtrak information board in New York City shows the Washington-bound train from New York as cancelled May 13, 2015 after an Amtrak train derailed in Philadelphia late on Tuesday May 12th.
Amtrak train derailment
Emergency workers search for passengers after an Amtrak train carrying 243 passengers from Washington, D.C. to New York derailed in north Philadelphia, May 12, 2015.
Amtrak train derails
A crime scene investigator looks inside a train car after a train wreck, Tuesday, in Philadephia, May 12, 2015.
Amtrak train derails
A man looks on at a police barrier near the wreckage of an Amtrak passenger train that derailed in north Philadelphia, May 12, 2015.
Amtrak train derails
Emergency personnel work inside an train car at the scene of an Amtrak train derailment in Philadelphia, May 12, 2015.
An Amtrak train headed to New York City derailed and crashed in Philadelphia.
Amtrak train derails
Emergency personnel work at the scene of an Amtrak train derailment in Philadelphia, Tuesday, May 12, 2015.
An Amtrak train headed to New York City derailed and crashed in Philadelphia.
Amtrak train derails
A police officer talks to bus passengers stopped at a emergency barrier near the wreckage of an Amtrak passenger train that derailed in north Philadelphia, May 12, 2015.
Amtrak train derails - survivor
Emergency personnel help passengers at the scene of the Amtrack train wreck, Tuesday, May 12, 2015, in Philadelphia. An Amtrak train headed to New York City derailed and crashed in Philadelphia.
Amtrak train derailment
Emergency personnel work the scene of the deadly Amtrack train wreck in Philadelphia, Tuesday, May 12, 2015. An Amtrak train headed to New York City derailed and tipped over in Philadelphia.
Amtrak train derails - investigation
Emergency personnel work at the scene of a deadly train wreck in Philadelphia, Tuesday, May 12, 2015.
Amtrak train derails
Passengers of an Amtrak train that crashed gather Tuesday, May 12, 2015, in Philadelphia. Train 188 was traveling from Washington to New York City.
Amtrak train derails - survivor
Emergency personnel help an injured passenger at the scene of an Amtrak train crash in Philadelphia, Tuesday, May 12, 2015. An Amtrak train headed to New York City derailed and crashed in Philadelphia.
Amtrak train derails - wreckage
Emergency personnel work at the scene of an Amtrak train crash, Tuesday in Philadelphia, May 12, 2015.
An Amtrak train headed to New York City derailed and crashed in Philadelphia.
Amtrak train derails - survivor
Emergency personnel help a passenger at the scene of an Amtrack train crash in Philadelphia,May 12, 2015.
Amtrak train derails - injured
Emergency personnel help a female passenger at the scene of an Amtrak train derailment and crash in Philadelphia, Tuesday, May 12, 2015.
Amtrak train derails
Rescue workers search for victims in the wreckage of a derailed Amtrak train in Philadelphia, May 12, 2015.
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.
Amtrak train derails
Emergency personnel carry a passenger on a stretcher from the scene of an Amtrak train derailment and crash in Philadelphia, Tuesday, May 12, 2015.
Amtrak train derails - wreckage
An Amtrak train crashed in Philadelphia, Tuesday, May 12, 2015. Train 188 was traveling from Washington to New York City carrying 243 passengers.