The driver of a train which crashed into a New Jersey station, killing a woman, suffered from undiagnosed sleep apnoea, it has been reported.
Officials said Thomas Gallagher, 48, was diagnosed with the condition after the derailment in September, according to AP.
A woman was killed by falling debris and 114 people were injured at Hoboken station.
Mr Gallagher told investigators he had no memory of the crash, but remembered waking up on the floor.
He was initially described as “critically injured” but was later said to have been well enough to cooperate with police.
An official says investigators are considering if Mr Gallagher’s alleged condition was a cause of the crash, AP reports.
The train was at the end of its hour-long southbound journey from Spring Valley, New York, when it hit the terminal at Hoboken station.
Witnesses described a scene of terror and chaos as the crash topped support columns in one of the busiest transit hubs in the New York area.
Following the crash, New York Governor Andrew Cuomo said it was obvious the train had come into the station too fast, but not why it had.
He added: “If there’s something to learn then we will be sure to learn it and incorporate that lesson.”
Sleep apnoea is described by the NHS as a relatively common condition where the walls of the throat relax and narrow during sleep, interrupting normal breathing.
As a result, the person may not get regular sleep.