Newly released CCTV footage shows the moment a Chicago train derailed and managed to plow its way up an escalator at O’Hare International Airport.

More than 30 people suffered minor injuries when the eight-car Blue Line subway train derailed around 3 a.m. Monday morning.

Chicago Train Derailment

A Chicago Transit Authority train car rests on an escalator at the O'Hare Airport station after derailing around 3 a.m. on March 24. (Kenneth Webster/Associated Press)

National Transportation Safety Board (NTSB) investigator Ted Turpin revealed Wednesday the operator admitted she "dozed off" before the collision, waking only when the train jumped off the tracks. 

Turpin said the operator, who had been on the job for only two months, acknowledged she'd previously fallen asleep on the job in February, too, when her train partially missed a station.

He said the woman, who was cooperating with the investigation, often worked an erratic schedule, filling in for other Chicago Transit Authority employees. 

"Her hours would vary every day," he said.

Turpin said the NTSB is investigating the woman's training, scheduling and disciplinary history.

Amalgamated Transit Union Local 308 president Robert Kelly said the operator claimed she had been working a lot of overtime recently and was “extremely tired” at the time of the crash.

On the video, which has no sound, two onlookers near the escalator watch as the train approaches, then sprint away as they realize it’s out of control and hurtling right at them. Both appear to get out of the way in time. 

Turpin said the crash caused about $6 million worth of damage.

Meanwhile Wednesday, crews were cutting apart the lead car of the eight-car train that was damaged during the crash, sending sparks into the air at typically busy station that remains closed.

With files from the Associated Press