PHILADELPHIA (CBSNewYork/AP) –Full Amtrak service between New York and Philadelphia was set to resume on Monday morning, Amtrak said.

Repairs from last weeks derailment were originally expected to run through Monday night, but the railroad said the job had been completed.

Investigators are trying to determine the reason for the train’s acceleration and sorting through conflicting reports about an object striking its windshield.

National Transportation Safety Board member Robert Sumwalt said on CBS’s “Face the Nation” on Sunday that he wanted to “downplay” the idea that damage to the windshield might have come from someone firing a shot at the train shortly before it flew off the tracks, killing eight people and injuring more than 200 others.

PHOTOS: Amtrak Train Derails In Philadelphia

“I’ve 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,” Sumwalt said.

Officials said an assistant conductor on the derailed train said she heard the Amtrak engineer talking with a regional train engineer and both said their trains had been hit by objects. But Sumwalt said the regional train engineer recalls no such conversation, and investigators had listened to the dispatch tape and heard no communications from the Amtrak engineer to the dispatch center to say that something had struck the train.

“But, nevertheless, we do have this mark on the windshield of the Amtrak train, so we certainly want to trace that lead down,” he told CNN’s “State of the Union.”

Sumwalt acknowledged, however, in an interview on Fox News Sunday that train engines are routinely struck by various projectiles without catastrophic consequences.

Investigators remain focused on the acceleration of the train as it approached the curve, finally reaching 106 mph as it entered the 50-mph stretch, and only managing to slow down slightly before the crash.

“The only way that an operable train can accelerate would be if the engineer pushed the throttle forward. And … the event recorder does record throttle movement. We will be looking at that to see if that corresponds to the increase in the speed of the train,” Sumwalt told CNN.

The Amtrak engineer, Queens resident Brandon Bostian, who was among those injured in the crash, has told authorities that he does not recall anything in the few minutes before it happened.

Meanwhile, almost 20 people injured in the train crash remain in Philadelphia hospitals, five in critical condition but all expected to survive.

Sumwalt said the agency had long called for inward-facing video cameras on trains which he said would help provide crucial information about such crashes. And he said the kind of next-generation speed control systems that Congress has ordered installed by the end of the year could have prevented countless accidents over the years. The systems use transponders, wireless radio and computers to prevent trains from going over the speed limit.

Amtrak has said it expected to restore limited service between Philadelphia and New York on Monday, with full service resuming on Tuesday. Amtrak officials did not immediately return messages from The Associated Press seeking an update Sunday.

The Federal Railroad Administration on Saturday ordered Amtrak to expand use of a speed-control system long in effect for southbound trains near the crash site to northbound trains in the same area. The agency also ordered the company to examine all curves along the Northeast Corridor, the busy stretch of tracks between Washington and Boston, and determine if more can be done to improve safety, and to increase speed limit signs along the route. Amtrak said it would immediately comply with all of the directives.

PAYOUT COULD BE LIMITED TO $200M

For the first time, Amtrak could face a $200 million payout to train crash victims — the limit set by Congress. But that may be too low to cover the costs of the eight lives lost and more than 200 people injured.

That payout cap for a single passenger rail incident was part of a late effort in 1997 to pass a law that would rescue Amtrak from financial ruin and help it one day become independent.

Adjusted for inflation, which the law does not consider, that amount would be just under $300 million now. And Amtrak is still far from independent.

An Associated Press review of past cases found that Amtrak never before has been liable for a $200 million payout for a single passenger rail incident. The Philadelphia crash could be the first time the liability ceiling — designed specifically for Amtrak — would actually apply to the railroad.

It’s not known how high the costs of victims’ deaths and injuries from Tuesday’s crash will run.

On Friday, an Amtrak employee filed the first lawsuit, asking for more than $150,000 in damages. Amtrak employees are not limited by the $200 million cap because it only applies to passengers.

“I don’t think Amtrak has ever faced a situation like this, and since they own the Northeast Corridor, they’re 100 percent on the hook,” said Frank Wilner, author of the book, “Amtrak: Past, Present, Future.”

Funeral services were to be held Monday, for two local victims of the derailment.

Services for real estate executive Laura Finamore were planned for 9:45 a.m. in Little Neck. Education software CEO Rachel Jacobs was to be laid to rest in suburban Detroit where she grew up.

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