It appears no one was at the controls of a CTA Blue Line train that barreled, head-on into another train filled with passengers during the morning rush on Monday.
Now federal investigators are trying to figure out how it all happened.
The empty four-car train with brake problems traveled from a rail yard for nearly a mile at 20-miles-an hour around 8 a.m. Monday.
It came to a stop after slamming into a standing train at the Harlem station.
Thirty-three people inside the standing train were hurt in the impact, as others yelled and scrambled to escape.
The injuries were not life threatening.
The National Transportation Safety Boardhas now stepped in.
It will try to find out how the train broke through two fail-safe switches.
Blue Line trains are not stopping at Harlem/Congress, Forest Park Branch, due to Monday’s train accident.
Service has resumed to Forest Park.
Shuttle buses are in place between Harlem/Harrison and Oak Park stations.
Residual delays are expected to affect Blue Line service. Allow extra travel time.