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The lead investigator into a deadly Amtrak derailment near Philadelphia said on Sunday that his team has ruled nothing out in its search for the cause of the crash.

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“We have not ruled anything out, nor have we ruled anything in,” National Transportation Safety Board (NTSB) member Robert Sumwalt told host Chris Wallace on “Fox News Sunday.”

“We’re looking at everything at this point,” he added.

Sumwalt appeared on four separate Sunday news shows and said that questions remained unsolved about Northeast Regional Train 188’s crash last Tuesday night.

Sumwalt said on ABC’s “This Week” that his agency would definitively discover what had prompted the train’s derailment, which killed eight passengers and injured at least 200 more.

“I think what we need to know, we need the traveling public to know that the NTSB is conducting a very thorough investigation, and we will get to the bottom of this, and we have to have positive train control implemented soon to keep things like this from happening in the future,” he told ABC host George Stephanopoulos.

Sumwalt echoed that proposal during his stop on Fox.

Positive train control technology, he argued, was vital for stopping trains traveling at dangerous speeds.

“It would have prevented this accident,” he said of positive train control existing on Amtrak’s Northeast Corridor.

Sumwalt additionally downplayed the possibility that a projectile may have helped derail the train Tuesday evening.

“We interviewed the dispatchers and we listened to the dispatch tape, and we heard no communications at all from the Amtrak engineer to the dispatch center to say something had struck the train,” he said on ABC.

“Nothing at all that he reported to the dispatch center,” he said of Train 188’s engineer, Brandon Bostian.

“I would agree with that,” Sumwalt replied to Wallace on “Fox News Sunday” when asked if projectiles often hit trains without causing major accidents.

Sumwalt said on Fox News that his agency is meeting the FBI on Monday to discuss their probe of the accident for projectile strikes.

He also said on ABC that the NTSB had conducted alcohol and drug testing on Bostian and requested his cell phone records.