The head NTSB investigator said that Amtrak Train 188's engineer did not report being struck. Shown: National Transportation Safety Board officials on the scene of Amtrak Train No. 188, which derailed Tuesday in Philadelphia, killing eight and injuring hundreds, in this handout photo provided by the board, May 13, 2015. Reuters/National Transportation Safety Board/Handout

Addressing rumors that Amtrak Train 188, which derailed in Philadelphia Tuesday, was hit by a projectile, Robert Sumwalt of the National Transportation Safety Board told CNN’s “State of the Union” there was "nothing, nothing at all from the Amtrak engineer to dispatch to say that his train had been struck.”

Sumwalt is the lead investigator into the derailment of an Amtrak train traveling from Washington to New York City that derailed in Philadelphia Tuesday night, killing eight and injuring more than 200 people.

The FBI will "be on the scene” to examine the train’s windshield, Sumwalt told CNN. He added that although the NTSB would still look into the possibility the train had been hit prior to the derailment, he didn’t think it was possible it had been fired upon.

“No, I’d like to downplay that part,” he told CBS’s “Face the Nation.” “I’ve now seen the fracture pattern. It looks like something about the size of a grapefruit, if you will. And it did not even penetrate the entire windshield.”

Amtrak Train No. 188 derailed going 100 mph around a curve, according to reports, and train engineer Brandon Bostian has told authorities he doesn’t remember what happened. His attorney has said Bostian has a concussion, and Sumwalt said Sunday that Bostian had been cooperative with NTSB investigators.

As for Bostian's memory loss, Sumwalt said, “That’s typical in some traumatic events like this."

The NTSB wants to know “what the management decisions were at Amtrak,” Sumwalt said, and if there had been decisions to install “positive train control” in some places on the track but not others. If positive train control and been “installed and operational,” Sumwalt said, “it would’ve prevented this accident.”

Amtrak announced full Northeast Corridor service would resume Monday morning, including service between Philadelphia and New York.