The Amtrak train that crashed in Philadelphia Tuesday night was traveling at more than 100 mph—double the posted limit—before it derailed, the National Transportation Safety Board said Wednesday.
The train was going 106 mph when its engineer applied emergency braking just seconds before the crash, said Robert Sumwalt, a board member of the NTSB. In a news conference Wednesday, he stressed that the agency could not conclude speed alone caused the accident.
The posted speed limit at the sharp left turn where the train derailed is 50 mph, lower than on either side of the curve. The area where the derailment occurred is known as Frankford Junction and lacks a speed control technology the NTSB has advocated, Sumwalt said.
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The train was headed to New York City from Washington when it derailed and tipped over in Philadelphia, mangling the front of it, killing at least seven people and injuring several more. Some passengers climbed out of windows to escape.
Philadelphia-area hospitals treated more than 200 patients after the derailment, officials said Wednesday, though they still do not have an accurate count of how many people remain missing.
The search site remains "very active," Philadelphia Mayor Michael Nutter said in a separate briefing Wednesday.
Samantha Phillips, the city's director of emergency management, told a news conference earlier Wednesday that officials were still trying to account for all of the people on the train's manifest, and she urged anyone who had been on the train and gotten off safely to contact Amtrak and register themselves.
As of Wednesday morning, some passengers were still reported to be missing. Rachel Jacobs, chief executive of online learning start-up ApprenNet, had been among the missing, but authorities later confirmed she was one of the fatalities.
Abid Gilani—a senior vice president at Wells Fargo— also died in the crash, the company said.
Nutter also said that the train's recorder—the rail equivalent of an aviation "black box"—had been recovered and was being analyzed by Amtrak in Delaware, though there was no information yet from the device.
"We will continue to do all we can until we have accounted for all the people we believe were on that train," Nutter said.
Sumwalt said the event recorders and a forward-facing video camera in the front of the train will both potentially provide data on what went wrong.
The piece of track where the train derailed lacked "positive train control," a technology meant to keep speed in check and prevent derailments, Sumwalt added. The NTSB has called for the technology, and Sumwalt said the accident might not have occurred had controls been installed.
Railroads are under congressional mandate to install the system on passenger routes by the end of the year.
Train 188, a Northeast Regional, had left Washington, D.C. The front of the train was going into a turn when it started to shake before coming to a sudden stop.
An Associated Press manager, Paul Cheung, was on the train and said he was watching Netflix when "the train started to decelerate, like someone had slammed the brake."
"Then suddenly you could see everything starting to shake," he said. "You could see people's stuff flying over me."
Cheung said another passenger urged him to escape from the back of his car, which he did. He said he saw passengers trying to escape through the windows of cars tipped on their side.
Former U.S. Rep. Patrick Murphy was on the train and said he helped people. He tweeted photos of firefighters helping other people in the wreckage.
"Pray for those injured," he said.
Amtrak said the train was carrying 238 passengers and five crew members. It said rail service on the busy Northeast Corridor between New York and Philadelphia was stopped.
Sen. Tom Carper, D-Del., was on the train before it derailed, he told CNBC on Wednesday. Carper regularly rides the train route.
"I know a lot of the customers and felt a very personal sense of loss from all this," Carper said.
In a statement issued by the White House, President Barack Obama said he was "shocked and deeply saddened" by news of the accident.
Minutes before the Amtrak derailment, a projectile went through the engineer's window in a Southeastern Pennsylvania Transportation Authority train in the same corridor, The Philadelphia Inquirer reported Wednesday. There was no immediate indication the incidents were related, and no injuries were reported.
Nutter said the projectile had "nothing to do" with the Amtrak derailment.
Another Amtrak train crashed on Sunday. That train, bound for New Orleans, struck a flatbed truck at a railway crossing in Amite, killing the truck's driver and injuring two people on the train.
In March, at least 55 people were injured when an Amtrak train collided with a tractor-trailer that was stuck on the tracks in North Carolina.
Port Richmond, the site of Tuesday's crash, is one of five neighborhoods in what's known as Philadelphia's River Wards, dense rowhouse neighborhoods located off the Delaware River.
—The Associated Press, NBC and CNBC staff contributed to this report.
Audio of police scanner after Amtrak derailment. (Caution: Content may be upsetting to some listeners)