The operator of a commuter train was "extremely tired'' when it crashed through a barrier and up an escalator at Chicago's O'Hare International Airport, the head of a transit union said Monday.
Robert Kelly, president of Amalgamated Transit Union Local 308, said the operator reported that she had worked a lot of overtime before the derailment. The operator's name was not released.
The derailment happened just before 3 a.m. Monday at the end of the Chicago Transit Authority's Blue Line at O'Haret. No one suffered life-threatening injuries
National Transportation Safety Board official Tim DePaepe said earlier that investigators had not drawn any conclusions about the cause of the accident and were looking into whether faulty brakes, signals or human error were factors.
The operator, who was still hospitalized, will be interviewed, DePaepe said, and investigators would examine her routine over the last few days.
Six people were listed in fair condition and 26 in good condition at three area hospitals, according to fire officials.
The train derailed around 2:50 a.m. CT as it was pulling into the O'Hare station, Chicago Fire Commissioner Jose Santiago said at a morning briefing.
"The train actually climbed over the last stop, jumped up on the sidewalk and then went up the stairs and escalator," Santiago said.
Chicago Transit Authority spokesman Brian Steele told reporters that authorities are trying to piece together what happened, but says the train was likely traveling too fast.
"We will be looking at everything — equipment, signals, the human factor," he said.
Service on the Blue Line was still suspended between O'Hare and Rosemont as the morning commute began, according to transit authority alerts. Buses were being used to get passengers to and from the airport.
The Chicago Transit Authority began a four-year, $492 million track overhaul on the Blue Line earlier this month.
Contributing: Donna Leinwand Leger; William M. Welch'; Associated Press