"This is the first crash of a Metro train where there are a large number of fatalities, so these crashes are very, very few and far between," Sweedler said. "But that doesn't mean that the greatest and best technology shouldn't be used to protect passengers when these rare events do occur."
"The NTSB is looking at operations, we're looking at maintenance, we're looking at the tracks," Hersman said. "We'll be looking at performance of the equipment as well as survival factors."
Homeland Security Department spokeswoman Amy Kudwa told The Associated Press that federal authorities had no indication of any terrorism connection at this point in the investigation.
The accident happened when a stopped Metro train, waiting for clearance into the Fort Totten station, was struck from behind by a second train, according to D.C. fire officials. It occurred at 4:59 p.m. on the city's red line in northeast Washington between the Takoma Park and Fort Totten stations.
A D.C. alert Monday evening said, "Metro reports that two trains collided and one train is on top of the other train."
From his seat in the second car of his train, passenger Brad Sander said, "We saw the first car go up in the air."
"I slid off my seat, and just fell on the floor, not injured, and we found the emergency exit, and jumped out, and I called 911, and tried to just attend to the injured," Sander told ABC News today.
Passenger Father Dave Bottoms could only watch as the train car he sat in plowed into a stopped train ahead, crumpling its frame and sending a "wave" of wreckage toward him.
"I began praying," Bottoms told "Good Morning America" today. "It slowed down about three seats in front of our area."
Bottoms said that when the screeching of the metal stopped, the screaming started -- a woman and a man in his car had been pinned under some collapsed seats.
"A few people released themselves and climbed over the wreckage," Bottoms said. "I heard her screaming. I talked to her, encouraged her."
Bottoms said he assured the woman that they were not going to leave her and then led the rest of the passengers in the Lord's prayer. After a passenger busted out a window with a fire extinguisher, a police officer climbed in and directed the passengers as they lifted the seats off the trapped woman.
Bottoms didn't see whether the woman got all the way out, but "her pulse was strong," he said. "She was quiet."
The woman was likely one of scores taken to hospitals following the horrific crash that D.C. officials called the deadliest in the Metro's history.
One of the victims is a female Metro employee, identified as Jeanice McMillan of Springfield, Va., by Metro spokesman Steve Taubenkibel. McMillan was driving the rear train. She had been running Metro trains only since December. Investigators plan to subpoena her cell phone records to see if she was distracted on the phone or texting at the time of the accident.
According to D.C. fire chief Dennis Rubin, the injured were taken to various hospitals, including Howard University Hospital and Washington Hospital Center. At least 50 were walking wounded, around 14 suffered non-life-threatening injuries, and six suffered critical injuries, he said.
Dr. Johnnie Ford, a Howard University Hospital emergency room physician, told the AP that a 14-year-old girl suffered two broken legs in the accident.