Investigators don't yet know why an Amtrak passenger train was moving at more than twice the allowed speed when it ran off the rails on a sharp curve and killed at least seven people, and the train's engineer has so far refused to speak to police. It was the deadliest U.S. train accident in nearly six years. 
 
While questions grew about why a track technology that would have prevented the train from going over the speed limit had not yet been installed as planned, the lawyer for the engineer said Thursday that his client didn't even remember Tuesday night's crash.
 
"He remembers coming into the curve. He remembers attempting to reduce speed and thereafter, he was knocked out,'' Robert Goggin told ABC. He said the last thing 32-year-old Brandon Bostian remembered was coming to, looking for his bag, retrieving his cellphone and calling for help.
 
Goggin said his client, who suffered a concussion and had 15 staples in his head, was distraught when he learned of the devastation. He said his client "cooperated fully'' with police and immediately consented to a blood test, and he believes his client's memory will likely return once the head injury subsides. 

The derailment happened along the country's busiest rail corridor between Washington and Boston, where the national passenger railway carries 11.6 million passengers a year. 
Amtrak suspended all service until further notice along the Philadelphia-to-New York stretch as investigators gather evidence. The shutdown has forced thousands of people to find other ways to travel.

Despite pressure from Congress and safety regulators, Amtrak had not installed along that section of track a technology that uses GPS, wireless radio and computers to prevent trains from going over the speed limit. 

The train was moving at 106 mph (170 kph) before it ran off the rails along a sharp curve where the speed limit drops to just 50 mph (80 kph), federal investigators have said.

The engineer applied the emergency brakes moments before the crash but slowed the train to only 102 mph (164 kph) by the time the locomotive's black box stopped recording data, said Robert Sumwalt, of the National Transportation Safety Board. The speed limit just before the bend is 80 mph (128 kph), he said.

Most of Amtrak's Northeast Corridor is equipped with what is called positive train control.
 
"Based on what we know right now, we feel that had such a system been installed in this section of track, this accident would not have occurred,'' Sumwalt said.
 
The engineer refused to give a statement to law enforcement, police said. Sumwalt said federal accident investigators want to talk to him but will give him a day or two to recover from the shock of the accident.
 
Mayor Michael Nutter told CNN there was "no way in the world'' the engineer should have been going that fast into the curve and called him "reckless and irresponsible.'' Sumwalt said Nutter's comments were "subjective'' and said investigators are not making any "judgment calls.''
 
More than 200 people aboard the Washington-to-New York train were injured in the crash. Passengers crawled out the windows of the toppled rail cars, many of them with broken bones and burns. 

Nutter said some people were unaccounted for but cautioned that some passengers listed on the Amtrak manifest might not have boarded the train, while others might not have checked in with authorities.
 
Amtrak inspected the stretch of track on Tuesday, just hours before the accident, and found no defects, the Federal Railroad Administration said. Besides the data recorder, the train had a video camera in its front end that could yield clues to what happened, Sumwalt said.
 
Seven years ago, Congress gave Amtrak and freight and commuter railroads until the end of this year to install positive train control technology on their trains and tracks. Amtrak had said it expected to finish installing it throughout its Northeast Corridor by the end of 2012. Amtrak officials didn't reply to questions from The Associated Press about why the technology hadn't been installed on the Philadelphia tracks. (AP)