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By Erik Ortiz and Tom Costello

Federal investigators encountered early problems in analyzing a recorder retrieved from the wreckage of the deadly commuter train crash in New Jersey, temporarily delaying details that might help explain why the train failed to slow before slamming into a packed station Thursday.

Investigators were unable to download the results of the recorder in the field, T. Bella Dinh-Zarr, vice chairwoman of the National Transportation Safety Board, said during a press conference on Friday. The recorder will instead be sent to its manufacturer for further analysis.

A second event recorder remained out of reach Friday as crews worked through removing debris that blocked access where part of the Hoboken station's canopy collapsed in Thursday morning's rush-hour chaos. A 34-year-old mother was killed on the platform and more than 100 others, mostly inside the train, were injured and treated for cuts and even broken bones.

Ultimately, the black boxes could yield a wealth of data, from train speed to brake use to throttle position. Investigators will be able to piece together what the engineer was — or wasn't — doing as he headed into the Hoboken Terminal.

Investigators carried out a toxicology exam of the train engineer, 48-year-old Thomas Gallagher. Those results are still pending. Gallagher was released from the hospital on Friday and has been cooperative, the NTSB said.

The NTSB hopes to interview all three crew members involved in the crash: the engineer, a conductor and a brakeman. However it may take time to learn more of what caused the crash, Dinh-Zarr said. Investigators expect to be combing through the scene for the next seven to ten days.

"We have a very methodical way that we speak to anyone involved in an accident to get as much information and as accurate information as we can," Dinh-Zarr, vice chairwoman of the NTSB, said on TODAY.

Recovering the box from the lead car is important because that’s where the engineer was stationed, Dinh-Zarr said.

Gallagher, a 29-year veteran of New Jersey Transit, had no "red flags" in his employment history prior to the crash, and he has no questionable medical or criminal records, sources told NBC News.

Related: New Jersey Transit Train Didn't Have Positive Train Control

"I suspect that it won't be very long before we have some answers," Homeland Security Secretary Jeh Johnson said Friday on MSNBC's "Morning Joe." "The motorman is alive. Presumably, he'll be interviewed at some point soon."

"At this point," Johnson added, "no suspicions of terrorism or foul play — anything of that nature."

Investigators plan to be at the site for the next seven to 10 days, the NTSB said.

NJ Transit train service was suspended again Friday in and out of Hoboken, a major hub that brings tens of thousands into New York City each day. Subway and light rail service was resumed at the terminal.