Sources tell NY1 that the engineer at the helm of the Metro-North train that derailed in the Bronx is going to be checked out for sleep apnea.
The news follows reports that William Rockefeller was under "highway hypnosis" before the crash, and that he was having trouble adjusting to an earlier shift.
Sleep apnea is a disorder that can cause breathing to stop and start during sleep.
Meanwhile, three passengers hurt in the crash filed a lawsuit against Rockefeller and Metro-North Thursday.
Their lawyer blamed the Metropolitan Transportation Authority for failing to implement a technology that he says would have slowed the train remotely.
In 2008, Congress passed a law requiring every rail system to have that technology by 2015.
"September was when they first started trying to put these systems into the trains," said Attorney Michael S. Lamonsoff. "Why did they wait seven years from the date of the act? Why did they wait 25 years or 23 years since they knew that the system existed and could have installed it into their trains?"
Others are questioning the placement of an MTA "alerter" system.
The system is designed to automatically sound off after 25 seconds and apply the brakes if there's no response from the engineer within 15 seconds.
It was installed in the rear locomotive of the Metro-North train, but Rockefeller was driving the train from the front car, where there was no alerter.