Rachel Jacobs, CEO of a start-up and a Jewish community activist, is among those killed in Tuesday's fatal train crash in Philadelphia.
The death toll climbed to seven on Wednesday, with more than 200 people injured, some critically.
The New York Times reported Wednesday that a friend of Jacobs, Michelle Kedem, had received a text message from Jacobs’ family confirming her death.
Data recorder recovered
Philadelphia's mayor said the train's data recorder has been recovered, but officials warned that the number of people unaccounted for was not yet confirmed after Tuesday night's crash and that search-and-rescue work was taking precedence over the investigation.
"It's a devastating scene," said Robert Sumwalt of the National Transportation Safety Board.
The rail corridor between New York and Washington remained closed as investigators looked for what went wrong. President Barack Obama called the derailment "a tragedy that touches us all."
Amtrak said the train was carrying 238 passengers and five crew members.
Amid fears that the death toll could rise, Mayor Michael Nutter said some passengers listed on the Amtrak manifest might not have boarded the train, while others might not have checked in with authorities.
The mayor said some of the seven train cars, including the engine, "completely overturned, on their side, ripped apart."
The train, traveling from Washington, D.C. to New York City, lurched to the side and flew off the tracks at a notorious curve not far from the scene of one of the nation's deadliest train wrecks more than 70 years ago.
Passengers scrambled through the windows of toppled cars to escape. At least 10 were hospitalized in critical condition. Injuries included burns and broken bones.
An Associated Press video software architect was among those killed. Jim Gaines, a 48-year-old father of two, had attended meetings in Washington. His death was confirmed by his wife, Jacqueline.
The train conductor survived and was expected to give a statement to police. The train also had a video camera in its front end that could yield clues to what happened, Sumwalt said.
Passenger Jillian Jorgensen, 27, said the train was going "fast enough for me to be worried" when it began a hard bank to the right. The train derailed, and the lights went out. Jorgensen said she "flew across the train" and landed underneath some seats.
Jorgensen said she managed to wriggle free as passengers screamed. She saw one man lying still, his face covered in blood, and a woman with a broken leg.
"It was terrifying and awful, and as it was happening it just did not feel like the kind of thing you could walk away from, so I feel very lucky," Jorgensen said in an email to The Associated Press. "The scene in the car I was in was total disarray and people were clearly in a great deal of pain."
The area where the derailment occurred is not far from the scene of one of the deadliest U.S. train accidents: the 1943 derailment of The Congressional Limited, from Washington to New York, which killed 79 people.
Amtrak said rail service on the Northeast Corridor between New York and Philadelphia had been stopped.
Former U.S. Rep. Patrick Murphy was on the train and tweeted photos of firefighters helping other people in the wreckage.
"Pray for those injured," he said.