Rachel Jacobs, a Manhattan resident and mother who had just started a new job in Philadelphia, was among those missing from the Amtrak train that derailed Tuesday night, a business colleague said.

Jacobs, listed as 39, is married to a management consultant in Manhattan and is the mother of a 2-year-old son, said Karl Okamoto, the co-founder and former CEO of a University City online learning start-up.

Jacobs was newly hired as CEO to replace Okamoto at the company, called ApprenNet, Okamoto said. She traveled to Philadelphia from Manhattan twice a week, he said.

Okamoto added that the company's COO and co-founder, Emily Foote, was at the crash scene as well as at churches and schools where survivors were being sheltered after the crash, showing people photographs of Jacobs and asking whether anyone had seen her.

Jacobs had left the Market Street office after meeting Tuesday evening and was headed for the train, which she was "almost certainly on," Okamoto said.

"She had contacted her husband to say she was boarding the train," he added.

Because Jacobs was traveling with a 10-trip ticket, which allows a person to get on trains without reservations, there would not have been a record of Jacobs traveling unless a conductor had scanned her ticket, Okamoto said.

And since the crash occurred soon after the train pulled out of 30th Street Station, Okamoto added, it's possible Jacobs' ticket hadn't been scanned.

That would leave her off the official list of people missing from the scene, a potential situation Okamoto and Foote wanted to rectify.

"We want to make sure authorities focus on finding her," he said.

Jacobs is a native of Huntington Woods, Mich., and a Swarthmore College graduate, according to the company website. She earned an MBA from Columbia Business School.

Okamoto said Jacobs had not decided whether to re-locate to Philadelphia

Jacobs previously worked as vice president of strategy and business development for an education tech company called Ascend Learning, according to the website.

That's how Okamoto met her, he said, explaining that ApprenNet had been doing business with Ascend.

"She was our customer before she became our colleague," he said.

Asked to describe Jacobs, Okamoto paused, then said, "Imagine the kind of person you'd let run the thing you created."

Then he added, "She's a leader. She's a deeply experienced industry veteran in education technology."

Maintaining ties to her native state, Jacobs is chair of the board of directors of Detroit Nation, a group of former residents engaged in economic development, cultural innovation and job creation in Southeastern Michigan.

When Okamoto was asked to provide more details about Jacobs, he cut off the conversation and said, "Let's find her first."